I absolutely love the SCUMM period of Lucasfilm Games (later LucasArts) development and this document gives insight into the game that started it all.
It's interesting to see that although the Edison family stayed much the same as their original incarnation, the player characters changed completely, with only the name "Sandy" remaining from the original conception.
Maniac Mansion was the first game created using the SCUMM scripting language, giving it its name "Script Creation Utility for Maniac Mansion." SCUMM was updated many times and used by LucasArts to make a plethora of games from 1986 to 1998 till it was retired in favor of GrimE which debuted in their game Grim Fandango.
The fact that this game continues to resonate with what is good in gaming hammers home to me that you don't need a massive corporation and 500 people to design an enduring game. Three men with nothing but an idea and creative freedom created an iconical game that people will continue to enjoy for years to come.
And hey -- we've got Day of the Tentacle now, too. And did you know I've got a Purple Tentacle tattoo?
A look at the original Maniac Mansion design doc [GoNintendo]