Were there a lot of inside jokes?

When Edward Norton is standing outside the closed clinic (about half-way through the movie) the old bum says to him, "You have to use your power when you have it!" And then they do a close-up on the bum. I was half-expecting it to be Ed Koch or somebody. Instead it seems like it was just some 80 year-old actor.

Didn't it seem like there was supposed to be some kind of joke?

Of course, the primary 'inside joke' is the fact that people used to joke about how much they wanted to "kill Barney" because he was sooo popular with the kids. This movie is clearly a riff on that meme.

There were a couple of other inside jokes I spotted but they've slipped my mind...