If you've never experienced a game with Eagles fans, you should probably consider yourself lucky. Why, you ask? Because the stereotypes are right. They really are an angry people. They also like mustaches.
Anyway, they're aren't easy to understand without experiencing them. They're like Vikings' fans in that the expect their team to fail. The difference is the anger, however. They get angry not only after the failure occurs, but before it does as well. This means that not only are they constantly angry, but the good plays don't really change their mood so much as delay it. And, since they are constantly angry about their team, they tend to lash out at anything and everything. For example, on Sunday, when Greg Lewis had a pass knocked out of his hands by Antoine Winfield, they went from yelling at the refs (when they thought he'd caught it), to yelling at Greg Lewis for dropping it (after the replays showed he'd dropped it) to yelling "Get up Lewis, you [redacted] you're not that hurt" when he was in obvious pain after separating his shoulder. So yeah, that's Eagles fans for you. If you're interested in more observations on their primitive subculture, Twins Geek attended the game and got to sit amongst them.
And speaking of subcultures, this picture comes to us courtesy of Deadspin. I'd be willing to bet that both of them left comments here after my post on Favre.