Jack Black is officially cool now with the kiddie set. The father of two young kids guest stars on a special episode of Nickelodeon's preschooler hit "Yo Gabba Gabba!" -- and ET has an exclusive look!

"It's a very special episode of 'Yo Gabba Gabba' where me -- Jack Black -- comes flying in on my little mini-bike and crash-lands in Yo Gabba Gabba land, and I'm a little worried and scared, and I find out it's okay, that everyone's just friends," he explains.

In the special episode, airing tomorrow at 1:30 p.m. ET/PT, Jack sings, dons host DJ Lance Rock's orange jumpsuit -- and teaches the characters and the viewers at home a new dancey dance called "The Disco Roll"!

"I have a two-year-old son named Samuel, and 'Yo Gabba Gabba''s one of our favorite shows," says Jack. "My wife Tanya really thought it would be awesome if I came on the show, and I was like, 'Yeah, you're right, good idea.'"

For those not in the know, "Yo Gabba Gabba" encourages its young audience to get interactive and get up and dance to the music, inspired by colorful characters (Muno the red cyclops, Foofa the pink flower bubble, Brobee the little green one, Toodee the blue cat-dragon and Plex the robot) who are all ready to sing, play and dance along with the viewers as soon as they hear the magic words, "Yo Gabba Gabba!" Stars have lined up to appear on the show, including Elijah Wood, Tony Hawk, Laila Ali, "Saturday Night Live" stars Andy Samberg and Rachel Dratch and more.

"I think there's some cool lessons in the Yo Gabba Gabba universe about sharing, and don't throw things at friends; just some good, basic lessons. It's helpful. I'll see the Yo Gabba Gabba team singing about 'don't bite your friends,' and I'll look at Sam to see if the lesson's hitting home. And he's really listening."

Watch ET for more with Jack Black!