Willow's enormous powers, even if she is not fully in control of them, forced the writers to figure out a way to keep her from being part of every fight.
Camden Toy also appears in the Season Four episode "Hush" as one of the "Gentlemen", in the Season Seven episode "Same Time, Same Place" as Gnarl, and in the Season Five Angel episode "Why We Fight" as "The Prince of Lies".