Christina Applegate, Maya Rudolph and Sean Hayes Christina Applegate, Maya Rudolph and Sean Hayes

Six years after saying goodbye to his Emmy-winning "Just Jack" alter ego on Will & Grace, Sean Hayes is returning to NBC. He'll be recurring on Smash and is developing his own comedy series. But first up comes an amusing arc as a passive-aggressive nemesis to Ava (Maya Rudolph) on Up All Night.

"My character, Walter, used to be Ava's musical accompanist," explains Hayes, who'll duet with Rudolph on a naughty jingle. "When Ava got the talk show that catapulted her to stardom, I assumed she would bring me along." When that didn't happen, Walter built up years of resentment. "We run into each other at a children's party and rekindle a friendship. It doesn't come out until later how angry I am."

Then it's on to three episodes of Smash, where he'll play Terrence Falls, a diva who is cast in the new production, "Liaisons." "My character comes in and isn't happy with anything," says Hayes, who'll butt heads with Megan Hilty's Ivy. "He tries to change the direction of the show." But don't expect a Will & Grace reunion with series star Debra Messing, with whom he's remained tight: "As far as I was told, we have no scenes [together]."

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