He seems to be a fan of superheroes and gets a little surprised when he sees Mr. Incredible using his powers when he was lifting his car and then after the death of Syndrome when the house blew up he was amazed by the actions that superheroes do.
Rusty is a minor character on the feature film The Incredibles. He's a little boy that rides a tricycle and wears a cap. He really loves superheroes. It's possible that he might be a neighbor to Mr. Incredible since he appeared on his street. When he sees Mr. Incredible lifting up his car in a angry manner, while using his powers he gets so surprised that he blew a bubble with his gum and then it just popped. He then appears again on Mr. Incredible's yard and he asks Rusty: "Well, what are you waiting for?" then Rusty responds: "I don't know something amazing, I guess". Then his last appearance in the movie is when Syndrome gets defeated and The Incredibles house blows up and after it blew up. Rusty says in a amazed way: "That was totally wicked". Which means that he really loves superheroes and appreciates what they do.
So far from the movie, Rusty seems to be shy, quiet, and a bit nosey. Then yet he is also a nice and respectful person. He's only appeared three times in the movie. It also hints that Rusty is curious about superheroes when he once saw Mr. Incredible use his powers while lifting his car in a very angry mood and was easily-surprised by this. He must be very inspired by superheroes actions and their powers. Also Mr. Incredible might be one of his biggest fan's in the film.