To get this, complete the Time Traveler's puzzle. This one was for me by far the hardest. I was stuck for an eternity when I discovered, how to go on. The easy part was to transform the dinosaur to oil - but then what? How to get the bucket?
Quick step guide through the maze (beware of spoilers!) (without getting all the artworks! This is just the solution of the puzzle)
- You're starting off with the three characters standing in front of some stones (stalactites/stalagmites) which block the way onward. The only one that gets through them is the Time Traveller with her special ability!
- Go on (and past the time machine) and up the first ladder you see. Head left and again through another barrier of stones. Adjust (behind this barrier) that one stone if you need it and jump up the ledge to take the fuse.
- Go all the way back and down the ladder. Now head right and go down the first ladder you see.
- Head left and install the fuse. The time machine now works!
- Go to the time machine and press X two times to skip the future and land into the preshistoric time.
- First things first. Now we will get the other two characters (who are still in front of those stones and can't pass them). Go on to the first ladder, climb it and head to the left. Notice how the stalactites/stalagmites aren't there yet?
- Take that rock from the left and push/pull it right beneath that dripping oil (?). Now the stalactites/stalagmites in the present time are gone and the other characters can join you!
- Still with the time traveler go back and down the ladder now head right. Skip the first ladder and when the path splits take the one down/left. Go on, down the ladder, jump the gap and visit the Neaderthal. Take one of his misshaped wheels (lol...) and place it just on the edge of that little gap on the right. Stay there.
- Switch to one of the other characters and have him travel to the future time. Go the same path as you did with the time traveler and on the bottom, go down the ladder. Now head right to that dinosaur machine and press the button. Now you stink like dinosaur!
- Quickly have that character travel back to prehistoric time, again the same way, down the ladder and to that dinosaur.
- Lure him out and then have the time traveler push a misshaped wheel onto the dinosaur. Now there will be oil in the future time you can use to activate the motor. But first, we need a bucket...
Here comes the tricky part
- Take a single character to the prehistoric time and go to the room where the bucket display would be in the future. There's a rock blocking a hole in the ground with water dripping down from above. Move the rock with a character, and switch back to the present time. Now here's a well with a bucket. Pull it and switch to the future where there is now a broken well and a single bucket on display at your disposal :) The real trick to getting this to work is to make sure you're holding down the grip/hold button (X) when you switch to the second character! Otherwise the first character will just let go of the rock when you switch and nothing will happen. The same thing of course for the second character who has to hold the well up with X while switching to the third character in order for him to receive the bucket.
- The bucket in hand, collect the oil and put in into that motor near the elevator. Ride the elevator up and push the tire onto the elevator. Ride it down.
- Now you have to push/pull the tire onto the time machine, go to the prehistoric time and push it again as far as possible. It will eventually roll down and the Neanderthal will receive his beloved wheel! Now we have to eliminate that son of a....... Muhahahah!
- That's quite easy. Again go all the way down to him and just push another of his own misshaped wheels onto his head. BAM!
- Travel to the future and look at that: The time traveler's now the best employee of all time. You can take that precious key now without getting anihilated by that annoying laser.
- Take the key and travel back to the present. Now you can open the door all the way to the left and the puzzle is solved!