When Ron Stoppable stumbled upon the cave where North kept all the memorabilia from the show, North decided to train Ron as the next Fearless Ferret after the boy persuades him to (Ron never actually having seen the show).
Kim was later able to show North the reality of his delusion, depressing North. They both went to the Fearless Ferret convention where Rudolph Farnsworth, another actor who played a villain on the show suffering from the same kind of delusion as North was attempting to attack it. North was thrilled to see the convention. Upon the villain's defeat, at meeting North again he appeared to immediately break through his own delusion and shake hands with Timothy as old friends, both choosing to sign autographs for adoring fans.
Behind the Scenes
Timothy North is heavily based on his voice actor, Adam West, with his role as the Fearless Ferret being an obvious take on the 1960's Batman show. Adam West played a similar role as the Gray Ghost on the Batman: The Animated Series and his mentoring of Ron, voiced by Will Friedle, mirrors the show Batman Beyond, which starred Friedle as Terry McGinnis.