David Hornsby (born December 1, 1975) is an American actor, screenwriter, and producer. He is best known for a recurring role as defrocked priest Matthew "Rickety Cricket" Mara on the FX comedy series It's Always Sunny in Philadelphia, for which he also writes and co-produces. Hornsby also had a regular role on the NBC comedy-crime series Good Girls (2018-2020). He is also the voice of Fanboy in the Nickelodeon animated TV series Fanboy & Chum Chum.