In 1999, he was cast in the comedy-drama television series "Jack & Jill", which aired on The WB channel for two seasons. He appeared as Eli in the TV show "Felicity" and television guest appearances followed including "Baywatch", "Everwood", and "Summerland". From 2002 to 2003, Rex starred in the first season of The WB's sitcom "What I Like About You". He later appeared on the Lifetime primetime telenovela Monarch Cove, which ran for fourteen episodes in 2006. From television into film, Rex has held the lead role in feature films including "Scary Movie" 3, 4, & 5, "Hotel California", "Karate Dog", "King of the Avenue", and "Superhero Movie". Rex most recently starred alongside comedian Nick Swardson in the Comedy Central show, "Typical Rick", which ran for two seasons from 2016 to 2017.