who plays dennis on it's always sunny
Glenn Howerton Glenn Franklin Howerton III (born April 13, 1976)[1] is an American actor, producer, and screenwriter. He is known for his roles as Dennis Reynolds in It's Always Sunny in Philadelphia, for which he is also a writer and executive producer,[2] and Jack Griffin in A.P. Bio, as well as the lead role in the short-lived sitcom That '80s Show.