American actor and singer. As an actor, he is known for his recurring role as Diggie Smalls on the Disney Channel sitcom Liv and Maddie, and for his role as Brad Majors in the 2016 Fox musical television film The Rocky Horror Picture Show: Let's Do the Time Warp Again. McCartan is also known as one half of the pop duo The Girl and the Dreamcatcher. McCartan also played Jason "J.D." Dean in the Los Angeles and the original off-Broadway versions of Heathers: The Musical. He also played Fiyero, the main love interest, in the Broadway production of Wicked.