David Nadelberg, Mo'Nique David Nadelberg, Mo'Nique

David Nadelberg is mortified. When he launched his critically acclaimed stage show Mortified a decade ago, he couldn't have imagined that he would eventually host a TV spinoff for the Sundance Channel.

"Certainly me being on camera was never part of the vision starting out," Nadelberg says. "I feel very exposed about the whole thing. It's not something I'm used to in life. That's been an interesting learning curve. It's like going through an awkward adolescence, learning to be on camera."

It's only fitting, then, that Nadelberg's new series, The Mortified Sessions, revolves around celebrities rediscovering and sharing embarrassing moments and artifacts from their youth. The show, which launches tonight at 8 p.m., kicks off with The Office's Ed Helms and Oscar-winning standup comedienne Mo'Nique.

A second episode, airing at 8:30 p.m., features Modern Family co-star Eric Stonestreet. Each star is asked to go through their childhood belongings and share items — photos, school reports, journal entries, home video — that may be embarrassing to look at now, but shines a spotlight on their upbringing.

"It doesn't matter who you are, we all have some artifacts from our past, and whether it embarrasses us or it's fun and unusual, it's a window into who we are," Nadelberg says.

Future participants include Bryan Cranston, Will Forte, Alanis Morissette, Margaret Cho, Cheryl Hines and married couple Megan Mullally and Nick Offerman. "They agree to this, and it sounds like a cute, fun show," Nadelberg says. "But Cheryl Hines kept saying that this felt like a therapy session."

Some stars show up with a mountain of archival material and others have just a few things. "We have a crack team of people who are assigned to help stars dig up stuff," Nadelberg says. "There are people like Ed Helms, who has everything saved. We could have done eight episodes with that guy. And then there are people like Mo'Nique with less, but that's part of the conversation. We see how they're less sentimental about certain things."

Mortified began as a stage experiment, as Nadelberg sent out a mass email to friends, asking them whether they had saved any artifacts from the past. "Those emails have not stopped arriving nine years later," he says.

Since then, the Mortified stage show has been replicated around the country and has been turned into a series of books. Besides The Mortified Sessions, Nadelberg is also working on a Mortified concert film. "We're not just building a piece of entertainment," he says. "It's a sense of community. The message of the show is all about inclusiveness."

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