One of my favorite sites on the web is How It Should Have Ended. They create alternate endings for popular movies (and occasionally video games) and often their ending makes more sense than the original movie's did. At the very least HISHE's is funnier than the original. I've been waiting (not so) patiently for them to do The Avengers, and they finally released it yesterday.
Here ya go:
If you're confused by the appearance of Superman & Batman, watching a few of the HISHE videos (you want to anyway, don't you?) will show you that they tend to pop up in these videos, usually to hilarious effect. This is one of my favorites: