As best I can recall, my introduction to the medium of comic books came when I was six years old. I was home from school, sick in bed with a bad cold or the flu or something. My dad went to the local drugstore to get some medicine, and when he returned, he also had with him a little treat that he hoped would cheer me up, or at least distract me in between puking sessions: a pair of what he called “funnybooks.” Which confused me, because they weren’t funny. But that’s beside the point. One was a collection of stories about Superman and his various friends, cousins, and pets. The other (which I found much more appealing, probably due to the semi-lurid cover art) was an issue of a series called Marvel Team-Up.
As the title suggests, the premise of this series was to combine two or more characters who wouldn’t have ordinarily crossed paths in their own titles, and then send them off on an adventure together. In the issue my dad got for me — which somehow is the only one of this series I’ve ever read — the action was played straight. Apparently, however, not every issue was so serious:

Spider-Man and the cast of Saturday Night Live? Wow, I’ve got to track that one down… that’s got to be a hoot. Especially if you read it drunk, which is probably how it was written. Click the pic to go to the image source and a synopsis.
Incidentally, I understand that most issues of Marvel Team-Up were self-contained stories. Naturally, that lone issue my dad got me, the only one I’ve ever read — which, to no one’s surprise I’m sure, I still have — was one of the rare two-parters. To this day, I have idea how Spidey manages to free the Scarlet Witch from Cotton Mather’s foul mind-controlling cross-power…