Mather Zickel (born March 10, 1974, in New York, New York) is an American actor, writer, and comedian, 6′ 0″ (183 cm) tall, who graduated from Harvard University and studied at the Juilliard School. He is a member of The Groundlings in Los Angeles and has been active since 1997, accumulating over 80 film and television credits. He is married to actress Melanie Lynskey and they have two children. His most notable film credits include a role in 21 Jump Street (2012, with Channing Tatum and Jonah Hill), a role in 22 Jump Street (2014), a role in Bad Neighbors (2014, with Seth Rogen and Zac Efron), a role in Bad Neighbors 2 (2016), and a role in The Nice Guys (2016, with Russell Crowe and Ryan Gosling). On television he is best known as a recurring character in It's Always Sunny in Philadelphia (2005–present), Childrens Hospital (2008–2016), Drunk History (2013–2019), and What We Do in the Shadows (2019–2025, FX), with additional credits in Arrested Development (2013), Brooklyn Nine-Nine (2015), Veep (2016), Shrill (2017), What If... (2021, Marvel), and The Afterparty (2022–2023, Peacock). He has also written and produced for Childrens Hospital and Drunk History, and directed episodes of What We Do in the Shadows.