Day of the Tentacle Remastered – Does It Include the Maniac Mansion Easter Egg?

It seems as though the list of achievements for Steam is the same as for the PS4 version, so some cross referencing of this list against your Steam achievements, plus this list of descriptions for all the secret ones should clue you in.

There are a few that are likely candidates, though:

• Chef - requires that you microwave the hamster in the original Maniac Mansion game within DOTT. Just booting the game is (another) achievement, but you actually have to play for a bit in order to get this one.
• Music Appreciation Award - after getting the fake barf, leave the stereo on until (or turn it back on before, accounts vary) returning to yesterday for the final showdown
• Alas, Our Lazy Speechwriters Didn't Cover This - talk to the founding fathers while they're out of the room in Hoagie's portion of the game. They're only gone until you take the quill, so if you grab it right away you might miss this one.
• ESRB Violation - use the fork on the cat while Laverne has both
• Most Annoying Guest Ever - ring the bell at the front desk 100 times
• Master Plumber - flush 50 objects through time, which is more than the required number to win
• Can't Win and Chew Gum at the Same Time - use the chattering teeth on Dead Cousin Ted in the future, before giving them to Washington in the past

There are a ton of secret achievements, though, so running your list against the linked lists is probably your best bet.

I managed to get the game running but needed to use DoubleFine Explorer to extract the files from the game. Point this tool at your installed game and go into the maniac folder. Extract all of these files and then point your ScummVM to the files.