He is introduced in the episode "Cry H.A.V.O.C.", catching Michelangelo as he falls from a roof and saving him. However, H.A.V.O.C. turn out to be a nefarious band of mutants, and their pleasant attitude toward the Turtles was an attempt to convince them to join.
Over the next few episodes, Raptor remained a constant threat to the Turtles because of his loyalty to Titanus. Along with the other members of H.A.V.O.C., his eventual whereabouts are unknown.