This achievement occurs during Episode 5 - Outatime
After Hill Vallley disappears you'll end up at a farm house, this achievement tasks you with interacting with the Cactus at every available time, the Cactus is to your right. Theres also the chance to pick up another achievement assuming you have the Algae cakes on you.
Do the following:
• Interact with Cactus.
• Walk up to "Scary Mary"s door and over the tripwire.
• Interact with Tripwire.
• Dialog (Edna): Any
• Dialog (Edna): Any
• Interact with Cactus
• Interact with the Tripwire.
• Dialog (Edna): "We spent today together."
• Dialog (Edna): "I brought something for you!"
•
Use Item "Algae Cakes" to equip.
• Interact with Edna (With Algae Cakes equipped.)
•
Green Gobblin' in Back to the Future: The Game - 30th Anniversary Edition (Xbox 360) unlocked.
• Interact with Cactus.
• Interact with Doc. (If Edna closed the window before you have the chance to do this, just go trigger the tripwire again.
• Dialog (Edna): "It's Emmett Brown!"
• Dialog (Emmett): "Shnookums".
• Interact with Cactus.
•
Use Item "Recording Device" to equip.
• Interact with Edna (With Recording Device equipped.)
• Interact with Cactus.
• Interact with Tripwire.
• Interact with Cactus.
• Walk back by the outhouse.
• Interact with Mop.
• Walk back to the front of the house.
•
Use Item "Mop" to equip.
• Interact with Cactus (With Mop equipped.)
• Walk to the left side of the house.
• Interact with Edna's Hat
•
Use Item Edna's Hat to equip.
• Interact with Cactus (With Edna's Hat equipped.)
• Dialog (Edna): "Tannen".
• Interact with Cactus.
• Walk over to the left side of the house.
• Interact with Saloon Sign.
• Walk over to the right side of the house.
•
Use Item "Saloon Sign" to equip.
• Interact with Outhouse (With Saloon Sign equipped.)
• Interact with Cactus.