Muldoon was born in San Pedro, California, the son of Deanna, a homemaker, and William Patrick Muldoon II, a personal injury lawyer. He is of Irish descent on his father's side and of Croatian descent on his mother's side.
Muldoon was the first actor to play the role of Austin Reed on Days of our Lives, a role which he played from 1992 to 1995 and September 2011 to July 2012. He had a role in the popular teen television series Saved by the Bell in 1991. His next big role was as the evil Richard Hart, on the prime time soap opera Melrose Place, from 1995 to 1996. He also played Edmund in the Patsy Rodenburg production of King Lear. He is perhaps most well known for his roles in 1997's Starship Troopers and 2007's Ice Spiders.
Birthday: September 27, 1968