If you want to know something about movies, visit www.imdb.org
There I found the available information about Indy 4:
And everything that already was realized with Maniac Mansion
IMDB/Maniac Mansion [TV-Series 1990-1993]
and IMDB/La Mansion de la niebla (Spain/Italy, 1972)
, which doesn't seem to have anything to do with Maniac Manion but the english title. But if you watch the cast, you can see a couple with the names Fred and Elsa. That's something, huh?
/Edit: F*ck... just realized that the woman in MM was called Edna... ok, never mind this and the last 2 lines...^^)
With the difference between a movie about DOTT and one for MM, I agree with Udvanoky. I would hate to watch DOTT with real actors, but Maniac Mansion could be really interesting as a Movie of that type...