Fiver is literally a guide, telling Hazel where to go. Hazel may not always listen, but that's his choice as the protagonist.
Wait, what? El-ahrairah isn't even a real character, so how can he be a guide? It's true that El-ahrairah doesn't just show up to tell the rabbits what to do. But he does serve as a model and ideal for the rabbits to strive after. In other words, he's a guide not by pointing out the road, but by being the destination they want to reach. (You can almost imagine the rabbits wearing little WWED bracelets—"What would El-ahrairah do?")