The show is about young late-20s, early-30s relationships involving two different couples in varying degrees of coupledom: the new couple and the almost-engaged couple breaking up. Harris' character, Barney, is the fifth wheel who's resentful of the whole situation.
Harris rose to fame on TV as a teen, playing the namesake doctor on "Doogie Howser, M.D."
As a child actor, Harris co-starred with Whoopi Goldberg in a drama called "Clara's Heart," for which he won a Golden Globe. He also received a Golden Globe nomination for his performance in "Doogie Howser M.D."
Harris had supporting roles in "Starship Troopers," "The Next Best Thing," "Undercover Brother," and "Harold & Kumar Go to White Castle."
There was a lot of speculation in the media that Harris was gay, but he hadn't come out, so Harris decided last fall to set the record straight and confirmed that he is indeed homosexual.
There were statements on the Web site Canada.com that claimed he had helped his "longtime sweetheart," actor David Burtka, land a part on "How I Met Your Mother," though those stories haven't been confirmed.