Philip McCadden is a Metro Police Department detective who first appeared in the episode, Mother's Day, investigating the murder of Gibbs's former mother-in-law's would-be fiance.
McCadden reappeared in Guilty Pleasure (episode) where he and Anthony DiNozzo formed a strong, temporary friendship due to the fact that DiNozzo wasn't on speaking terms with Timothy McGee. Tony and McCadden's friendship got off to a good start due to the fact that both men shared a common love for movies, even referencing some movies during the case. Tony dubbed McCadden McC while McGee referred to the two men's bromance as T-Cad but cracks later began appearing in the friendship when McCadden told Tony that he could do better and began insulting McGee, calling McGee a geek while referring to Ziva as a Cupcake.
This ultimately prompted Tony to make up with McGee and break off his friendship with McCadden and presumably stop speaking to McCadden for good.