RPGs are about Superman and the Teen Titans

I was lurking on RPG StackExchange where I happened upon a post asking how to integrate high-powered NPCs with groups of lower-level PCs. There were a number of good answers already, but I thought of an example that I personally use when trying to do just that.

Comic books provide a great answer to your question with an example. When Brainiac invaded the Earth, Superman and the Justice League went off to fight him. Meanwhile, the Teen Titans go around town saving people, preventing other villains from escaping the asylum, prevent the dam from breaking, and making their high school exams. Your high powered NPCs are the "Justice League": Superman, Batman, Wonder Woman, etc., and the PCs are the Teen Titans. Both are engaged in the same event (Brainiac attack) yet they deal with completely different elements. Then as they gain XP, your party will join the Justice League while some of the "kids" stay back and deal with the "small stuff"... Simple but an example I used myself.