The first time we see the fighting satyr Coach Gleeson Hedge race into battle, he's attacking Dylan, the evil storm spirit. Piper is falling, and Hedge leaps at Dylan, yelling to Jason, "Save her! I got this!" (2.70) before disappearing with Dylan.
We have to admit that when we first read this, we assumed that Coach Hedge knew what he was doing. He said, "I got this!" after all. If he said he could fight a storm spirit, who are we to doubt him?
Of course, over the course of the book, we learn that Hedge is constantly saying he's got things he hasn't got, and always going into fights where he can't win. He's overconfident and kind of nutty; satyrs just aren't that tough. Dylan turns him into a satyr-sicle, and he's frozen for several days until the heroes free him. In the battle with the giant Enceladus, Hedge gets knocked out instantly and spends most of the fight out cold with his hooves and goat butt in the air.
So we were was fooled, but we don't think we were stupid. After all, how could we have known Hedge wasn't a hero? Piper and Leo and Jason don't look like they can defeat giants or save the world, but they do it anyway. It's really hard to identify which heroes are foolhardy and which are the real deal.
In fact, Hedge, by imitating the real deal, manages to winkingly point out that the real deal is not, maybe, all that real. Taking on overwhelming odds seems more likely to land you in trouble than to result in saving the world. Hedge—goat legs and all—is a kind of comedic, realistic mirror image of Piper, Jason, and Leo. Attacking a giant isn't likely to work out very well for them either, after all, but they're the stars of the book so it does. Hedge helps draw our attention to the fact that the world is all kinds of unpredictable when it comes to our beloved demigods.