The Future isn't Written
Returned home. Story related, cannot be missed.
Emmett Finds His Muse
Emmett completes his spectacular failure at the Expo. Story related, cannot be missed.
Restored Edna's memory. Story related, cannot be missed.
Raising the Bar
Prevented the Great Hill Valley Fire.
Story related, cannot be missed.
Treated Desert Edna to an algae cake.
As you're going about your way in the Expo, the presentation roster on stage will change, allowing different people to go on stage and make a presentation. One of those names belongs to Hostile Guy and his algae cakes. Once he's on stage, simply hurry over to his booth and snatch the box.
Fast forward to alternate 1931. While coaxing Old Edna out of the house you'll have the chance to give her something. Once she asks what it is, select the cakes in your inventory, and hand them over.
A Prickly Pair
Had a conversation with a cactus.
This is a prickly trophy indeed. There are a lot of chances to converse with said cactus, and it looks like you need to use all of them.
-As soon as you're free to move. (Doc shushes you)
-Choose the cactus as the item you brought for Edna.
-Once after getting Edna outside.
-Once Edna is in the burned out DeLorean
-Once as soon as Edna is out of the DeLorean.
-Talk to it after putting the mop on.
-Then put the hat on triggering a cutscene.
-Once after she remembers Tannen. (Before you put the sign up)
-Then once after putting the Saloon sign on the outhouse.
Complete the glass house maze without going back up the stairs.
Once you've talked to Diver about the whereabouts of Emmett, he'll direct you toward the Glass House Maze. Once there you'll see that it's a sliding wall puzzle. Here's what you have to do;
-Go down the stairs.
-Open 2nd yellow.
-Open green. (Cutscene)
-Open 2nd purple.
-Walk to the end of the maze.
You'll get this once you enter the House of the Future via the bookcase.
Impersonated three people over the phone.
While browsing the Expo, go up to the Phone Booth of the Future and examine it. You'll get the booth's number and learn a bit about it too. Once you have the number, head over to the House of the Future and call the booth using the panel on the wall and pressing the green button. When Trixie answers you'll have four voices to choose from. Simply use the three that aren't your own.
Get it on Tape
Recorded everyone at the Expo.
Once you've looked at the recording plant at the police booth, head over to the House of the future and grab the plant off of the table and bring it back. Select it in your inventory, and replace the one on the booth. Now that you have the recording plant here is a list, in order, of who you need to record;
-Doc/Diver (After glass maze)
-Edna (Via phone confession)
Get your money's worth at the Expo.
At the Expo there are a bunch of things to examine, and make sure you've gotten your tickets from Trixie. Here is a list;
-Police Booth (Plant Recorder, Breath Analyzer, Future Weapon)
-Phone Booth of the Future
-Diver/Enlightenment Under the Sea Ride
-House of the Future (And everything inside)
Defuse the standoff while climbing to the second floor no more than two times.
This is easy after putting some thought into it before you progress. Here's what you have to do;
Busted a move, 80's style.
Whilst being nosy at the Expo, head over to the Theremin Booth. Just examine it a few times (7 to be exact) to get Marty to bust out an MJ.