The original Maniac Mansion game, as it was made for PC, can be played in Day of the Tentacle simply by using Weird Ed's computer.
Originally, there was not going to be voice acting and there was going to be six playable characters. Apart from Bernard, Hoagie and Laverne, there would also be Moonglow, Chester and Razor. Moonglow and Razor were omitted early on, while Chester became the basis of the twins Jed and Ned Edison. When Myst (1993) came out, it popularized voice acting in games, so the creative team decided to make Day of the Tentacle,their first "talkie game". The disk version only had voice acting in the introduction, while the CD-ROM version had talking throughout the game.
Lead artist Peter Chan always puts the name of his children in games he is working on. The name 'Zach' as seen on the license plate of the broken car in the parking lot at the mansion is the name of his son who was born the same year. Benjamin Franklin's room has a penguin calendar with a January date circled, which is the birthday of Chan's wife.
The classical piece of music that opens the game is the Wilhelm Tell Overture.
The entire opening credits scene was created by Kyle Balda during his internship at LucasArts. It was his first job working on a video game, and although it was quite a responsibility, the team was unanimously impressed by his efforts.