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