In the original version, the license plate is the name of the first feature film by George Lucas, THX-1138
In the original version of Maniac Mansion, a Star Wars poster is on the arcade wall
If you rotate the telescope all the way left, an alien will jump in front of your view. This is a Jaggi, the race of hostile aliens from Rescue on Fractalus!, the first game by LucasArts (alongside Ballblazer)
Edna's comment when she throws you in the dungeon is a lot more tame in the NES version
In the NES version of Maniac Mansion, Edna will think dead cousin Ted is on the phone when you call her
The Nintendo censors thought the conversation between Ed and Edna implied cannibalism, so the NES version states he hasn't slept in 5 years, which Douglas Crockford reasons is the reason Fred's never seen in his bedroom
The NES conversion team at LucasArts tried to sneak as many adult themes past the Nintendo censors while changing the content to adhere to Nintendo's strict moral standards of the time. So the game "Kill Thrill" was changed to the sexually suggestive title "Tuna Diver"
The medical diagram in the NES version reads "pretty brains" in retaliation to Nintendo making LucasArts change the phrase "getting your pretty brains sucked out"
One of the possible numbers for contacting the Meteor Police is an obvious reference to THX 1138.
In the NES version of the game, the pennant (the sprite of which was removed, but the hotspot oddly remains) reads "SCUMM U. RAH!", SCUMM U. being the training program for rookie SCUMM developers.
Both of these works of art appear in a storeroom in Castle Brunwald in Indiana Jones and the Last Crusade.
In the NES version of the game, the broken record reads as "Loom soundtrack record." Upon putting it on the Victrola, what sounds like the first few notes of The Glass City theme plays.
A poster for Zak McKracken appears in the arcade room, (Enhanced version only) and in Zak McKracken a poster for Maniac Mansion appears in the pawn shop. Also, the chainsaw found in the kitchen is useless because it is out of gas, a joke which pays off in Zak McKracken when you find a useless can of gas on Mars that is for "chainsaws only."
The debut of the famous Chuck the plant, who would later appear in such games as Indiana Jones and the Last Crusade, as well as Day of the Tentacle, the sequel to Maniac Mansion.