Never played Maniac Mansion on the NES, and haven't played the original in so long that I'd fail to spot the differences anyway. But a fantastic article penned by former Lucasfilm/Lucasarts employee Douglas Crockford shows just how many changes they had to make to the adventure classic to get it published on the NES, and how batshit loco some of those changes were.
Howie Rubin of Jaleco (the company that was going to publish the game under license) advised us the that the baddest bad word is Kill. The central activity in most Nintendo games is killing things. The image and the act are good, but the word is bad, even if the word does not suggest the image or the act.
The mansion contains a number of arcade video games. One was called KILL THRILL. The name had to be changed. Doug Glen, our Director of Marketing, suggested that we change it to MUFF DIVER, which I thought was a pretty good idea.
See? Good reading. The Expurgation of Maniac Mansion for the Nintendo Entertainment System [via Dtoid]