Which actor plays Liz Lemon's ex-boyfriend Dennis Duffy?

Dean Winters plays Liz Lemon’s ex-boyfriend Dennis Duffy on 30 Rock.

Dennis is introduced as Liz’s former boyfriend and quickly becomes one of the show’s most memorable recurring nuisances. He is a self-styled “Beeper King” whose aggressive confidence, questionable judgment and habit of reappearing in Liz’s life make him a particularly bad match for her.

Winters plays Dennis as both obnoxious and oddly magnetic. The character’s shameless persistence lets the show explore Liz’s tendency to revisit disastrous relationships, even when she knows exactly why they ended. Dennis also functions as a comic contrast to Liz’s more self-aware but equally chaotic romantic choices.

Dean Winters was already known for dramatic television work, including Ryan O’Reily on HBO’s Oz, before appearing on 30 Rock. He later became widely recognizable as the personification of “Mayhem” in Allstate commercials. The other listed actors are associated with 30 Rock, but they play different characters: Steve Buscemi appears as Lenny Wosniak, Cheyenne Jackson plays Danny Baker, and Will Forte plays Paul L’Astname.