lol Mamma Mia...I've only ever seen the film version, but apparently the stage version was also quite successful. The songs are very infectious, even though it's not the best film by any stretch (Pierce Brosnan trying to sing? What?), but the songs can get stuck in your head so easily (especially Dancing Queen and the titular Mamma Mia, in my opinion). I found it funny in the movie all the people that appear out of nowhere (more than I felt with any other musical film I'd ever seen)
I can understand why it would be a movie that would cheer you up, though, all those famous people having fun and the catchy songs.
Hmm...even though I'm through with the brief quasi-obsession I had with it two years ago, The Rocky Horror Picture Show I guess is kind of a guilty pleasure of mine. I know it's not a great film, nor do I claim it to be, but the songs are so catchy and the humor is silly, but somehow it works. It's not a film or a musical that I love, but I do enjoy the songs quite a bit. And it does have nods to other films and things, which are kind of fun. And even though it's silly, there are songs that are not so silly, like Science Fiction Double Feature. And then there are the fun ones like Time Warp and Bless My Soul.
There might be some other guilty pleasure that I can't recall right now, but I'd say this is definitely one of mine.