Reminders
Do Not Skip Cutscenes - Missable Achievement
Always use the "Fast Flush" option (open inventory, select item, then select character) to gain progress towards the 50 flush cumulative achievement.
Commands are written in Bold and items/objects you interact with are in Italics.
Walkthrough
Everything you need to know about the storyline of the game can be summed up in this one quote:
Dr. Fred: Step one. Find plans. Step two. Save world. Step three. Get out of my house! Let's get cracking.
We're going to start off by completing step one while collecting as many items we need to interact with along the way.
Find Plans
After the opening cutscene you'll be in control of Bernard, the loveable nerd, in the Lobby of the Mansion.
Let's get the most annoying achievement out of the way.
Use Service Bell - Repeat this 100 times.
Pick up Flier.
Pick up Dime (in pay phone).
Pick up Help-Wanted sign.
Open Office Door and enter office.
Pick up Swiss Bankbook.
Open Drawer.
Pick Up Booboo-B-Gone (inside drawer).
Open Portrait.
Return to Lobby.
Open Grandfather Clock.
After a cutscene, you'll find yourself in the Basement of the Mansion.
Pick up Paper (on To-Do Bulletin Board).
After a few cutscenes you'll now have control of another playable character, Hoagie, the roadie who is now stuck in the past (surprise surprise. . . things didn't go exactly as planned).
You also have the ability to toggle between Hoagie and Bernard as well as pass items between characters. Before progressing the storyline, we're going to get another annoying achievement out of the way. Do NOTHING with Hoagie for about 5 minutes, as idling with Hoagie causes him to pull out a sandwich and eat it.
Switch back to Bernard.
Give Flier to Hoagie (reminder - use the Fast Flush option).
Give Help-wanted sign to Hoagie.
Give Textbook to Hoagie.
Switch back to Hoagie. Now that our "plans" have become more complicated, we're going to walk through the mansion, collecting and interacting with as many objects as possible with Hoagie.
Hoagie
Follow path to Inn.
Open Mailbox.
Pick Up Letter.
Open Door and enter Inn.
Talk to Mummy (1/3 characters talked to Dead Cousin Ted).
Open Grandfather Clock and enter Basement.
Pick up Left-Handed Hammer.
Give Help-Wanted Sign to Red Edison.
Pick Up Lab Coat.
Use Patient Application with Bulletin Board.
Exit Basement and head upstairs.
Open Door (first door on the right) and enter George Washington's Bedroom.
Push George's Bed.
Pull Cord.
While the maid is cleaning George's Bedroom, exit to Hall.
Pick Up Soap (on the maid's cart).
Continue around the Hall to last door on left.
Open Door and enter Ben Franklin's Room.
Pick up Wine Bottle.
Exit Ben's Room into hallway and head up Stairs to Third Floor.
Use Textbook on Horse.
Pick up Dentures.
Open Door on left and enter Art Room.
Here Ned & Jed are sculpting and/or modeling.
Use Left-Handed Hammer with Barrel.
Exit back to Third Floor Hallway.
Head upstairs to Attic (Jed & Ned's Room).
Use Ned's Bed (bottom left bed).
Use Squeaky Mattress with Jed's Bed (top bed).
Use Squeaky Mattress.
Pick up Squeaky Mouse Toy.
Pick Up Red Paint.
Walk to Window exiting you out onto the Roof.
Walk to Chimney (1/3 characters climb through the chimney).
You've now found yourself in the Main Hall with a few historic characters.
Walk to Swinging door and enter Kitchen.
Pick Up Spaghetti.
Pick Up Oil.
By now you should've picked up 15 things that don't belong to you. . . sticky fingers.
Open door and enter Storage Closet
Pick Up Bucket.
Open Cabinet.
Pick Up Brush (inside cabinet).
Exit Storage Closet returning to Kitchen.
Use Bucket with Water Pump.
Use Soap with Bucket of Water.
You're now back in the Main Hall and you've visited almost every room in the mansion as Hoagie. Time to screw with a bit of history.
Exit Main Hall, exit Front Door, and follow the path back around to the Outhouses.
Use Red Paint on Kumquat Tree.
Follow path back around towards Inn. This time we'll head over to the Dirty Carriage.
Use Bucket of Soapy Water with Carriage.
After the cutscene ends, head back inside the Inn and enter the Main Hall.
Use Flier with Suggestion Box.
Give Wine Bottle to Thomas Jefferson.
Talk to George Washington selecting the following dialog options:
Hoagie: Whoa, you're like George Washington?
Hoagie: Whoa.
Hoagie: Is it true about you and the Cherry Tree?
Hoagie: I bet you've lost it. You couldn't cut down a tree to save your grandmother?
After the cutscene you should earn:
We've pretty much done everything you can do with Hoagie at this time, and you now have the ability to control the third character, Laverne, the insane med-student, who is stuck in the future. Before moving on to the next character, we're going to Fast Flush a few items to Bernard.
Give Textbook to Bernard.
Give Red Paint to Bernard.
Give Brush to Bernard.
Give Letter to Bernard.
Switch to Laverne.
Laverne
Laverne starts "locked up" in the Kennel.
Talk to Tentacle Guard and select the following dialog option:
Laverne: Oh. . . I don't feel so good. . .
You'll now find yourself in the Tentacle Doctor's Office, and after a short scene, you'll be alone.
Pick Up Tentacle Chart.
Walk to Door (all doors open automatically in the future, yay).
You're now in the Lobby.
Walk to Front Door (door on left) which gets you locked up. . . again.
Talk to Tentacle Guard again, this time selecting the following dialog options:
Laverne: I have to go to the bathroom!
You'll now find yourself outside the Front Door.
Walk to Path (head right).
Now we're outside of the Chron-A-John and can share items with our friends.
Give Scalpel to Bernard (yes. . . I'm also VERY scared that Laverne has been running around with a sharp object).
Give Tentacle Chart to Hoagie.
We're going to leave Laverne here for a while as we've done everything we can do with Laverne at this time. This will be one long bathroom trip!
Next we'll switch to Bernard and have him run through the Mansion, collecting and interacting with everything he can at this time.
Switch to Bernard.
Bernard
This is a great time to save your game. We're not at a point-of-no-return, but this would be a good place to reload from, if needed.
The last time we left, our hero nerdy friend, Bernard was in the Basement.
Head Upstairs into the Lobby then continue upstairs to the Second Floor of the Mansion.
Open Door (the door labeled "W") and enter Honeymoon Suite.
Close Door.
Pick Up Keys (found in door lock).
Use Television.
Use Television a second time.
Open Door and return back to the Second Floor Hallway.
Continue down Hallway.
Open Second Door (the door labeled "R") and enter Dwayne's Room.
Use Letter with Dwayne.
Pick Up Disappearing Ink.
Pick Up Flag Gun.
Leave Dwayne's room, returning back to the Second Floor Hallway.
Open Third Door (the door labeled "F") and enter Green Tentacle's Room.
Push Speaker.
Pick Up Videotape.
Use On/Off Button on Stereo.
Leave Stereo On - Missable achievement
Leave Green Tentacle's Room returning back to the Second Floor Hallway.
Head Upstairs to Third Floor.
Open Door on right and enter Weird Ed's Room.
Pick Up Hamster.
Use Textbook with Stamp Album.
Use Disappearing Ink on Weird Ed (1/5 squirt people with disappearing ink).
Use Disappearing Ink on Stamp Album.
Oopsies. . . I guess not every joke is funny to everyone. You now find yourself back in the Third Floor Hallway.
Pick Up Stamp.
Pick Up Stamp Album.
Return back to Weird Ed's Room.
Use Stamp Album with Weird Ed.
We now have the first opportunity to diverge from the main storyline and play the prequel game, Maniac Mansion, to earn the 2 achievements in this game. You can choose to play this game now, play it later on in the storyline, or skip the game entirely during the storyline and reload the save you recently made. For those wanting to play this game now, expand the spoiler text below. For those choosing to wait until later, Maniac Mansion's complete walkthrough can easily be found on its own page.
--------------------------------
*** Spoiler - click to reveal ***Use Computer.Manic Mansion
*REMINDER* If at any time you are lost as to what item is where, use the What Is command and scroll around the screen to find the proper item.
NOTE - Commands are written in Bold and items/objects you interact with are in Italics.
Select "Start Game"
Select "Dave", "Syd", and "Razor" as your playable characters.
Start Game.
Playable Character DAVE (Default)
Walk to Left to front of Mansion.
Pick Up Door Mat.
Pick Up Key.
Unlock Front Door with Key and enter Mansion.
Open Door (only door in entryway of the mansion) and enter Kitchen.
Walk to Right and get captured.
New Kid select Razor.
Playable Character RAZOR
*NOTE* If at any point you have a cutscene with Weird Ed saying he's hungry or the doorbell rings, avoid the Kitchen and Stairs, so you don't get captured or killed.
Walk to Left and enter Mansion.
Walk to Kitchen.
Walk to Right.
Open Door and enter Dining Room.
Walk to Right, all the way through the Dining Room.
Open Door and enter Pantry.
Pick Up Fruit Drink.
Exit Pantry, walking back through the Dining Room, the Kitchen and back into the Entryway.
Walk to Stairs, and proceed upstairs.
Walk to Left.
Open Door and enter Art Room.
Pick Up Bowl of Wax Fruit.
Exit Art Room.
Walk to Steel Security Door (Blue Door).
Walk to Right.
Walk to Stairs, all the way upstairs.
Walk to Left.
Give Bowl of Wax Fruit to Green Tentacle.
Give Fruit Drink to Green Tentacle.
Walk to Left.
Walk to Stairs and proceed upstairs.
Walk to Right.
Open Fourth Door and enter Room.
New Kid select Syd.
CREATE A SAVE GAME HERE - This next portion requires proper timing so you don't get captured.
Playable Character SYD
Walk to Left, to front of Mansion.
Use Door Bell.
New Kid select Razor.
Playable Character RAZOR
Wait about 10 seconds (Ed needs to leave his bedroom and head downstairs) then exit the room you are in.
Open Door to the left and enter Ed's Bedroom.
Pick Up Hamster and exit Ed's Bedroom.
Enter room to your Right (room you were previously in).
Wait about 10 seconds (Ed needs to return to his bedroom) then exit the room you are in.
Walk to Left, heading back downstairs continuing Right, down the Second Staircase, continuing Left through the Steel Security Door (blue door), and down the Stairs to the Entryway.
Walk to Kitchen (door on the left at the bottom of the staircase.
Open Microwave Oven.
Use Hamster in Microwave Oven.
Close Microwave Oven.
Turn on Microwave Oven.
ChefCook the hamster in Maniac Mansion (Don't try this at home, kids!)

Now that you've finished all achievements in Maniac Mansion, press start and exit to return to Day of the Tentacle.
--------------------------------
Exit Weird Ed's Room and head upstairs to Archive Room.
Open Door and enter Attic Prison.
Walk to Window to get out on to the Roof.
Pick Up Crank.
Walk to Chimney (2/3 characters climb through the chimney) and you'll find yourself in the Convention Room.
Open Grating.
Use Scalpel with Ooze the Clown.
Pick Up Box O' Laughs.
Move over to the Right side of the room.
Walk to Vat O' Teeth. The chattering teeth will "jump" down. Follow the teeth over to the Left until the teeth get caught in the open grate.
Pick Up Trapped Teeth.
Use Flag Gun with Cigar Lighter (looks like a gun).
Talk to Cigar Salesmen selecting the following dialog:
Bernard: Nice cigars.
Bernard: Sure. Lay one of those Havana babies on me.
Use Disappearing Ink on Cigar Salesman (2/5 squirt people with disappearing ink).
Open Door and exit to the Lobby of the Mansion.
Pick Up Fake Barf.
You should have picked up 30 items now. . . you klepto.
Open Front Door and exit outside.
Head to Parking Lot.
Use Keys with Man in Ski Mask.
Use Disappearing Ink on Man in Ski Mask (3/5 squirt people with disappearing ink).
Use Brush with Filthy Old Car.
Return back to Lobby of the Mansion.
Use Crowbar with Gum with a Dime Stuck in it.
Use Gum. . . YECK!!!
Head back upstairs to Second Floor and enter the Honeymoon Suite.
Use Disappearing Ink on Sleeping Conventioneer (4/5 squirt people with disappearing ink).
Use Dime with FickleFingers Coin Slot.
Use second Dime with FickleFingers Coin Slot.
Pick Up Sweater. . . DOUBLE YECK!!!
Return back to Hallway.
Give Hamster to Hoagie (using Fast Flush).
Open Ice machine.
Use Hamster in Ice Machine.
Use Crowbar with Candy Machine.
Pick Up Quarters (yeah. . . no idea how his pants are still on).
Head back downstairs and enter the Convention Room.
Walk to Swinging Door and enter the Diner.
Pick Up Fork.
Pick Up Decaf Coffee.
Pick Up Coffee.
Use Fork (or any other metal item) with Microwave.
Open Door and enter Laundry Room.
Open Dryer.
Use Sweater in Dryer.
Use Quarters in Coin Slot.
Open Cabinet.
Pick Up Funnel.
Leave the Laundry room, heading back through the Kitchen, through the Convention Room and into the Lobby.
Walk to Dark Passageway (Grandfather Clock).
You're now in the Basement with Dr. Fred.
Use Decaf Coffee with Dr. Fred.
Head Upstairs, upstairs again, around the hallway, and upstairs again to the Third Floor Hallway.
Open Door on Left and enter the Security Office.
Use Disappearing Ink on Nurse Edna (5/5 squirt people with disappearing ink).
Push Nurse Edna.
Use Videotape with VCR.
Use VCR.
Select Record (Red Square).
Select Rewind (Double Arrows pointing to Left).
Toggle to EP (Small Lever on Right).
Select Play (Single Arrow pointing Right).
Wait for video to finish (yes, it's in slow motion). You don't need to write down or memorize the code.
Select Eject (Arrows pointing Up).
Exit back to Hallway and head upstairs to Archive Room.
Talk to IRS Agents, selecting the following dialog:
Bernard: Are you guys brothers?
Now head back downstairs, all the way to the Lobby, and enter the Office.
Open Safe.
Pick Up Contract.
Leave office and enter the Convention Room.
Walk to Fireplace taking you up to the Roof.
Walk to Window taking you into the Attic Prison.
Pick Up Rope (Bernard really has magic pants).
Walk to Window taking you back onto the Roof.
Use Rope with Pully.
Walk to Chimney.
You'll now be back in the Convention Room. Exit Convention Room and head outside.
Talk to Dead Cousin Ted (2/3 characters talked to Dead Cousin Ted).
Use Red Paint with Dead Cousin Ted.
Use Dangling Rope with Dead Cousin Ted.
Return back to the Roof. You'll need to go back into the Mansion, into the Convention Room, and though the Fireplace to get to the Roof.
Pull Rope.
Oopsies. . . you find yourself back outside. Again, you'll need to head back up to the Roof, via the Fireplace.
Walk to Window, entering the Attic Prison.
Use Ted with Doctor Fred.
Use Rope with Doctor Fred.
Walk to Window, taking you back onto the Roof.
Pull Rope.
Now we're in the Basement with an unconscious Dr. Fred.
Use Funnel with Dr. Fred.
Use Coffee with Dr. Fred.
We've now finished as much as we can at this point with Bernard. Before switching to another character we're going to get a couple of random achievements out of the way.
Use Decaf Coffee with Coffee.
Use Booboo-B-Gone with Disappearing Ink.
Use Booboo-B-Gone with Contract.
Use Booboo-B-Gone with Red Paint.
Now it's time to Fast Flush items to our friends.
Give Contract to Hoagie.
Give Stamp to Hoagie.
Give Cigar Lighter to Hoagie.
Give Cigar to Hoagie.
Give Chattering Teeth to Laverne.
Give Booboo-B-Gone to Laverne.
Give Box O' Laughs to Laverne.
Give Fake Barf to Laverne.
Give Crank to Laverne.
Give Fork to Laverne.
Switch to Hoagie.
Hoagie
Give Spaghetti to Laverne.
Give Can Opener to Laverne.
Give Squeaky Mouse Toy to Laverne.
Give Dentures to Laverne.
In total we'll need to Fast Flush 50 items and we should already have quite a few out of the 50 done, but let's go ahead and grind out the remaining ones now. You can send the same item back and forth between characters, but I found it easiest/fastest to send 10+ items to one person, then switch characters and send those same 10+ items to the next character. Doesn't really matter which items you flush for the 50, but note that not all items are flushable (i.e. Coffee, Crowbar, Videotape). Once you have Fast Flushed 50 items, this achievement should unlock:
*** Spoiler - click to reveal ***After all the flushes, check your inventory against this table to make sure the proper characters have the items they need. If the item isn't listed below, any character can hold it as we have no further use for the item. Bernard | Hoagie | Laverne |
Swiss Bankbook | Oil | Can Opener |
| Lab Coat | Dentures |
| Tentacle Chart | Chattering Teeth |
| Cigar | Soggy Spaghetti |
| Cigar Lighter | Squeaky Mouse Toy |
| Stamp | Fake Barf |
| Contract | Fork |
| | Booboo-B-Gone |
| | Box O' Laughs |
| | Crank |
Now we've got a quick chore for Hoagie.
Follow path back to Inn and enter into the Lobby. Head upstairs to Second Floor Hallway.
Open Door (second door) and enter Betsy Ross's Room.
Use Tentacle Chart with Patterns.
Exit Room and head back downstairs to Main Hall. We're going to leave Hoagie here, while we play as Laverne.
Switch to Laverne.
Laverne
This is another great time to create a new save of your game (use a new save location). Again, we're not at a point-of-no-return, but this would be a good place to reload from, if needed.
We last left Laverne outside her Chron-O-John. . . many, many moons ago.
Follow path back around to Front Yard and enter former motel. You'll find yourself back inside the Kennel, locked up.
Talk to Tentacle Guard and select the following dialog option:
Laverne: Oh. . . I don't feel so good. . .
And again you'll be taken to the Tentacle Doctor's Office.
Walk to Door exiting the Doctor's Office, placing you in the Lobby.
Walk to Door taking you into the Registration Room (this would be the Main Hall or Convention Room for Bernard or Hoagie).
Walk to Fireplace taking you up onto the Roof (3/3 characters climb through the chimney).
WWSCD?Climb through the chimney with all three kids

Use Crank with Crank Box.
Use Crank.
Pick Up Flag.
Use Flag (So so so Pretty!!!).
Walk to Chimney, taking you back down to the Registration Hall.
Talk to Tentacle (blue one).
Return back to Lobby and head upstairs to Second Floor Hallway.
Look at Ice Machine.
Pick Up Frozen Hamster.
Walk to Door (the door labeled "W").
Use Can Opener with Time Capsule.
Pick Up Vinegar.
Exit back to Hallway.
Walk to Door (the door labeled "R").
Pick Up Extension Cord.
Pick Up Roller Skates.
Talk to Mummy (3/3 characters talked to Dead Cousin Ted).
Missable achievement - Make sure you pay attention to the proper order here - Roller Skates with Mummy, Push Mummy, Find Mummy, then place Name Tag on mummy - as doing this is a different order caused this next achievement not to unlock.
Use Roller Skates with Mummy.
Push Mummy.
Exit Room returning to Second Floor Hallway and help downstairs to Lobby.
Use Name Tag with Mummy.
Walk to Stairs, follow the Hallway around and continue up to the Third Floor.
Time to pretty up Dead Cousin Ted.
Use Chattering Teeth on Mummy.
Use Dentures on Mummy.
Use Box O' Laughs on Mummy.
Use Soggy Noodles on Mummy.
Use Fork with Mummy's Hair. (Ummm. . . that was flushed in the Chron-O-John. . . BLECK!!!)
Use Fake Barf with Harold. (Super pretty human in pink tutu.)
Walk to Highly Restricted Judging Area (Right).
Talk to Judges selecting the dialog option:
Hey, when are you guys going to judge Best Hair?
Talk to Judges again selecting the dialog option:
Hey, when are you guys going to judge Best Smile?
Talk to Judges a third time selecting the dialog option:
Hey, when are you guys going to judge Best Laugh?
You'll find yourself back in the room you found Dead Cousin Ted in.
Exit Room and head back downstairs to Lobby and exit the former Motel.
Follow the path to the Right and you'll see a cat by the fence.
Walk to Cat (looks like it's a scaredy-cat).
Use Booboo-B-Gone with Fence.
Use Squeaky Mouse Toy with Cat.
Use Fork with Cat.
Follow path back to Chron-O-John.
Use Extension Cord with Plug.
Use Extension Cord with Window.
Follow path back into the former Motel and head into the Registration Room.
Walk to Door (to the Right of the Kennel Door) and enter Kitchen.
Use Frozen Hamster with Microwave.
Use Cold Wet Hamster with Microwave.
Walk to Door and enter Laundry Room.
Open Dryer.
Pick Up Sweater.
Use Sweater with Cold Wet Hamster.
Exit Laundry Room and head back into the Registration Room.
Walk to Kennel.
You're automatically in a conversation with the Guard Tentacle. To quickly end the creepy conversation select the dialog option:
Laverne: I'm here by accident. Bye.
Use Dinner Certificate with Guard Tentacle.
Use Switch.
Use Cat (or is it a skunk???).
Exit Kennel and return to Lobby.
Open Grandfather Clock.
Walk to Grandfather Clock, taking you downstairs to the Basement.
Use Extension Cord with Outlet.
Use Toasty Warm Hamster with Generator.
Use Built-In Shop Vac with Mouse Hole.
Open Hatch.
Pick Up Dust Ball.
Use Dusty Warm Hamster with Generator.
We've now done everything we can with Laverne, but before switching to Hoagie let's share some items.
Give Chattering Teeth to Hoagie.
Give Vinegar to Hoagie.
Switch to Hoagie.
Hoagie
Before progressing any farther, check that you have acquired the Chattering Teeth with Mummy achievement. We will be using the item, thus passing the point-of-no-return, for that achievement.
This is also another great place to create a new save of your game. If you've got all the above mentioned achievements you can override your save location, but, in my opinion, it's always best to create a new save, just in case.
We last left our roadie in the Main Hall with a few of the founding fathers. Head over to the right towards George Washington.
Use Exploding Cigar with George Washington.
Use Chattering Teeth with George Washington.
Pick Up Blanket.
Exit the Main Hall back to the Lobby, and head all the way upstairs to the Attic.
Walk to Window and out onto the Roof.
Use Blanket with Chimney.
Now head back through the Window, all the way downstairs and outside. Follow the path outside towards the Outhouses.
Talk to John Hancock.
Return back to the Inn and head into the Main Hall.
Pick Up Gold-Plated Quill Pen.
Use Gold-Plated Quill Pen with Contract.
After a brief cutscene you'll find yourself in the Lobby.
Walk to Grandfather Clock.
Give Oil to Red Edison.
Give Vinegar to Red Edison.
Before progressing any further, check that you have acquired the Sign Contract with Gold-Plated Quill Pen achievement. We will be using the item, thus passing the point-of-no-return, for that achievement.
Give Gold-plated Quill Pen to Red Edison.
Pick Up Battery.
You should now have picked up a total of 45 items that don't belong to you, earning you:
Head back up to Lobby, take the stairs up to the Second Floor, and return to Ben Franklin's Bedroom (third door).
Give Lab Coat to Ben Franklin.
After a couple of cutscenes:
Use Battery with Kite.
Push Kite.
After another couple of cutscenes:
Pick Up Fully-Charged Battery.
Walk to Outhouses.
Missable achievement here. Make sure you do the following in the proper order; Battery with Chron-O-John first, then Battery with Plug.
Use Battery with Chron-O-John.
Use Battery with Plug.
We've now done everything we can with Hoagie. We're going to need to take control of Bernard again, but before doing so let's Fast Flush an item.
Give Contract to Bernard.
Switch to Bernard.
Bernard
Talk to Dr. Fred selecting the following dialog options:
Bernard: Oh forget it. I'll get rid of purple tentacle myself.
Bernard: I'm getting Purple Tentacle declared insane and arrested.
That's it for Bernard, so off to Fast Flush.
Give Signed Contract to Hoagie.
Switch to Hoagie.
Hoagie
Use Stamp with Signed Contract.
Follow path around back to Inn.
Use Signed Contract with Mailbox.
We're done with Hoagie again.
Switch to Bernard.
Bernard
This is the final point-of-no-return. Double check all above achievements have unlocked and/or all warnings were headed.
Head upstairs to Lobby and enter the Office.
Use phone.
After a brief cutscene the following achievement will unlock:
If you followed the warning about leaving the stereo on, you'll also unlock:
SAVE THE WORLD
After a few cutscenes you'll find yourself ready for step two: Save the World.
You'll find yourself in control of your character (yeah. . . not exactly sure what to call this creature except "Thing") in the Honeymoon Suite.
Exit Room and head into the Second Floor Hallway.
Open Dwayne's Room (labeled "R") and now you become Mini-Thing.
As Mini-Thing, enter Dwayne's Room.
Walk to Mouse Hole (this must be done before you become Big-Thing).
Now you're in Green Tentacle's Room. Wait until you become Big-Thing.
Pick Up Bowling Ball.
Open Door. (Where'd he go!?)
This is the last opportunity you have to play Maniac Mansion without reloading a save.
Head downstairs through the Grandfather Clock and into the Basement.
Use Bowling Ball with Purple Tentacles.
Talk to Purple Tentacle, selecting the following dialog options:
Thing: Just what is it that you have against humans, anyways?
Thing: Sounds like that's all Dr. Fred's fault, really.
Thing: You're pretty handy with that ray gun.
Thing: Why don't you zap Dr. Fred if you hate him so much?
This will take you to the final cutscene which, as long as you heeded the warning throughout this walkthrough, you should gain two achievements.
After sitting through all the credits you should unlock:
The final achievement is buggy, as it SHOULD unlock after the previous achievement unlocks, but it doesn't. Instead go ahead and exit the game, doing a full "Quit" of the game (
, scroll down and select "Quit"). Now load back into the game, selecting any of your save games and the final achievement should unlock.
OCDGet all other achievements in the game

Congratulations!!! You've now completed this classic Point & Click adventure game. I'll leave you with these very wise words of Purple Tentacle:
Purple Tentacle: I feel like I could. . . like I could. . . like I could. . . TAKE ON THE WORLD!!
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