Jack Stone is a famous Afro Kung Fu movie star.
He (probably) runs a karate school, which is revealed to be a lazy and non-active karate school where the students goofed off the whole time and learned absolutely nothing. It's implied the Jack Stone who teaches at that school is an imposter since not only he looks significantly less easy on the eyes, lankier, and out of shape than the Jack Stone the kids saw in the movies, but when asked why he called a movie he made in the 70s his latest movie, he bluffs it off to imply he's a long-retired actor despite the kids watching a movie he starred in relatively recently. That and it's weird how a still-famous movie actor would run a martial arts school in a random city like Emilyville (then-named Wizardville).
He fought Khan in the movie Penny and her friends enjoyed watching[1].