After last week's episode, which featured Criss singing Katy Perry's "Teenage Dream," the actor joined the likes of Lea Michele, Cory Monteith and Dianna Agron as a series regular on the FOX hit musical comedy.
"Darren has become such a sensation in one week, which I love," executive producer Ryan Murphy told the Web site AfterElton.com. "I think there's a hunger for him and a positive relationship role model. He'll definitely continue through the year and longer. We just signed a deal with him."
Attending the New York premiere of Harry Potter Monday was a dream come true for the actor, whose YouTube video "A Very Potter Musical" is a viral hit with more than 3 million views.
"A lot of people who know me as Harry, it's kind of weird, because I'm not Harry Potter," Criss told MTV News.
When asked how he felt about walking the red carpet at the Harry Potter premiere, Criss joked, "I'm just a huge fan. All these fans outside, I should be out there. This is just a terrible mix-up. There's been some terrible mistake."