Well, with Kirby, he might be a mixed basket with his sexual orientation.
He seems to love feet, which, is a well known popular fetish for gays. (Look it up, but uh, NSFW)
It seems that he was a parody of a common closeted high school athlete. Basically, in a desperate bid to hide his sexual orientation, he joined sports and worked hard to befriend the others.
ALSO, there might be a bit more. Perhaps Kirby also joined so he can have access to the locker rooms... so he can watch others change. lol