Justin Cavallero is one of Chad Dickson's friends who is also a Teen Ninja. He appears in Operation: E.L.E.C.T.I.O.N.S. with a speaking role: he tells Chad that the Gallagher Elementary School students have no chance against their Hendry Middle Schoolforces, and then they are both sent back to their seats (being in a classroom). Later during the battle between both schools, he interrupts Chad as he's sweet-talking a girl with news that they might have a problem defeating the elementary kids. Then he is told to get ready on Chad's bike - and not to "scratch it or nothing". He makes no further appearances in the episode, it was unknown if he joined the battle or not.
He also appears in Operation: T.R.E.A.T.Y., when Chad and Numbuh 1 are in a Teen hangout underneath a mini-mart. He reminds Chad that no kids are allowed to know about their hangouts as he called Numbuh 1 stupid. Numbuh 1 angrily asks who are you calling stupid so he and several other Teen Ninjas chase him out. They intend to shoot him out of the sky; when Kids Next Door aviators tell him to stand down because they're in a "no-fly zone", he tells them that the guys they're chasing (Chad and Numbuh 1) stole his little brother's bike. It is unclear whether or not this was a lie, or if he really does have a little brother. However what ever the purpose is he needed some help from Kids Next Door aviators to shoot them down