Kenan Thompson

Mirror, mirror on the wall. Who has the best costume of them all?

That's the question the first annual Hub Halloween Bash aims to answer. The two-hour special, hosted by Saturday Night Live's Kenan Thompson, features children from across the country competing in a star-studded costume contest with the winner nabbing $25,000 and a walk-on role on the Daytime Emmy-winning series R.L. Stine's The Haunting Hour: The Series.

The costumes will be judged by a celebrity panel, featuring Martha Stewart,Hal Sparks and Coco Jones, in six different categories: Mad Genius, Everyday Stuff, Animal Kingdom, Howlarious, Sooktacular, Blast from the Past. Not to mention the most coveted title of all, Best in Bash.

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But the children won't be the only ones dressed up. "I'm gonna be in a bunch of costumes," Thompson tells TVGuide.com. (His outfits include Dracula and a mummy.) And after years of SNL Thompson is used to many costume changes, though his favorites from the sketch show are his old man costumes. 
"They make me laugh," Thompson says. When it comes to Halloween, Thompson holds a special place in his heart for the years he dressed up as Mr. T and the The Incredible Hulk, even though his Hulk was "just the mask with a plastic tarp over it."

For the Hub Halloween Bash, the judges will join Thompson in sporting their Halloween best, especially Stewart, who didn't hold back with her Glinda the Good Witch costume. The two-hour special will also feature appearances by Bill Nye the Science GuyNolan GouldRico Rodriguez and more. On hand to perform will be teen pop sensations Cody Simpson and Fifth Harmony, in addition to illusionist Nathan Burton.

Watch an exclusive sneak peek of The Hub Halloween Bash below before it airs Saturday at 8/7c on the Hub Network.