Maniac Mansion NES was the first adventure game I ever completed (Space Quest II was the first I ever played, but I never completed it until much later), so I'm always happy to see someone mention it.
Speaking of that, I've been collecting the Flashback dedicated consoles and managed to snag the Adventure Flashback Blast! for a good price on Mercari. It contains games based on Disney and Lucasfilm properties, and surprisingly it also includes the NES version of Maniac Mansion.
I managed to talk to Ron and Gary at PAX East when I was working at the Double Fine booth, and Ron said that most people tell him that the NES was the system they used when playing Maniac Mansion.
It was awesome to finally meet them, as they're two of my inspirations (Ron for gaming and coding, and Gary for art - especially comic art). Now if I can meet Tim Schafer (he wasn't at PAX East unfortunately, but I did get to work with Spaff), Steve Purcell, Michael Land, Michael Stemmle, Peter McConnell, and Bill Tiller, I'd be able to die happy.