Some of this is even exemplified in “Secret Wars.” Considered, the first ever massive company-wide crossover event, it featured the Fantastic Four, Spider-Man, the X-Men, the Avengers, and a host of their crappy villains (plus Doctor Doom, Enchantress, and Magneto)
transported to a world made of cobbled-together parts of other worlds
(so...generic rock planet plus one freaked-out Denver) on the whim of an
all-powerful entity curious about the nature of good and evil (if this seems
familiar, it's because this is almost the plot of a classic episode of Star
Trek, and it is exactly the plot of two others. I can only suppose that
Lincoln and Kah'less were too busy in the mid-eighties to really help out the
X-Men with this one.).
So, they fight a few times, all seems lost, but then it's not. Repeat three times. Colossus falls in love because he's the star of a one-man production of the tear-jerking motion picture, “Steel Vaginas.” Johnny Storm gets his Fantastic Four drama in the X-Men drama, and X-Men get X-Men drama in the Fantastic Four drama. Oh, and Spider-Man punks the X-Men (not all of them; the speed necessary to punk all of the X-Men in a single crossover event would take a pair of quantum-entangled Flashes or one very pissed-off Hulk) and finds out he is Advanced Alien Costume Making Machine/Advanced Alien Archnemesis Making Machine colorblind (the consequences of which are never explored, not even a little bit).
Anyway, Dr. Doom--that killjoy--decides that instead of roleplaying this module out to the end, he's going to buy an unlicensed third-party sourcebook and some loaded dice so he can metagame like a motherfucker, then re-write his stats so he's a god.
Doctor Doom is a hell of a powergamer and destroys the other players, which works for him until his will falters and he reconstitutes—by accident, his power is so vast—the vanquished heroes and they kick his ass with the help of The Beyonder. Have I mentioned The Beyonder?