Originally, there was not going to be voice acting and there would be six playable characters at the start. Apart from Bernard, Hoagie and Laverne, there would also be Razor (the female musician from Maniac Mansion (1987)), Moonglow (a short character in baggy clothes) and Chester (a beat poet). Because of design issues and memory limitations, Moonglow and Razor were omitted early on, while Chester became the basis for the twins Jed and Ned Edison. When Myst (1993) came out, it popularized voice acting in games, and when the game's original deadline could not be met, the creative team decided to make use of the extra development time 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.
The original Maniac Mansion (1987) game, as it was made for PC, can be played in Day of the Tentacle simply by using Weird Ed's computer.
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 William Tell Overture.
Lip syncing software did not exist in the 90s when the game was made, although the makers did have a software program that created mouth movements based on the volume of the voices, meaning that the characters' mouths would only move if they had lines.