It may have only been a rumor when it was first reported, but it's 100% confirmed now: Neil Patrick Harris will appear this spring on Glee.

According to a show insider, "fans will love" the guest-starring stint (as if there was ever any doubt!). What role will the How I Met Your Mother star portray on the musical comedy?

Sources tell E! News that Harris will play a character who is "really funny and really mean... much more of the Dr. Horrible variety than Doogie Howser, M.D."

While Harris might be the most exciting name to sign on for Glee, he's far from the only one.

Idina Menzel, Molly Shannon and Olivia Newton-John will all guest star on at least one episode of the show. It returns with new installments on April 13.

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.