Why Are Hilary Duff and Joel McHale Throwing Down on the Set of Community?

Starlet teases her turn as a mean girl on this Thursday's episode of the NBC hit

Joel McHale? Supernice guy. Hilary Duff? Really sweet gal. So how come when we hit the Community set—where Hilary is guesting this week—she and Joel were trading some funny verbal jabs?

Turns out Hilary has a little beef with Joel's awesome E! show called The Soup...

On the Community set for Hilary's "mean girl" themed episode, we noticed something strange while chatting with both Duff and McHale—each time they'd pass each other, one them would make a cute quip about her sister Haylie.

Turns out, this was some minor comedy backlash after Joel made a joke on The Soup about Haylie's cheesetastic onetime MTV reality show Legally Blonde The Musical: The Search for Elle Woods. (See it here.)

"It's hilarious," Hilary laughed. "I told Joel when I met him, 'My sister and her boyfriend (actor Nick Zano) want to just run up to you and push you down, just knock you over!' They're totally kidding, they love him and they love The Soup—[the joke on the show] really wasn't mean at all."

So how did the Soup host/Community star react? "Joel said, 'Oh no! Did I say something mean about your sister?'" Hilary recalled. "I said, 'Yeah you did! Now you're going to deal with me.'"

And this seemingly sweet girl is certainly a force to be reckoned with on this Thursday's Community. "Meghan is the lead bitch in the bitch crew at Greendale," Hilary told us. "Things get crazy." How crazy, you ask? Crazy enough to make Abed (Danny Pudi), yes, Abed, the biggest, meanest bitch of 'em all.

"Abed gets a little meaner than I do," Hilary revealed. "He says something about me having dandruff, which if someone said that to me in real life, I'd probably have to hit them. That is so awful! Meghan gets put in her place with the insults that Abed gives her, then [spoiler alert!] he ends up saving her in the end and helping Meghan regain her queen bee position. But it doesn't make her any less of a bitch."

Here's a little taste from Duff of how bad things get between the battling bitches, which includes Shirley (Yvette Nicole Brown), Annie (Alison Brie) and Britta (Gillian Jacobs), too: "Meghan says [Abed] looks like his mom was a lizard who was raped by a Muppet!" Oh wow.

But don't worry about Abed. As Yvette puts it: "He's a weapon of mass humiliation. He will find your mass and completely zero in on it and target it, and destroy you." "He's basically like an insult robot." Gillian teased. Take that, mean girls of the world!

Hilary (who cozied up to Dan—and Vanessa—on Gossip Girl last season) said she's happy to be back on TV.

"I am such a fan of this show," she gushed. "They just called and asked if I wanted to do a quick thing on Community, and I said yeah. I love this show; it's so funny, the characters get to have so much fun, and there have been so many great guest stars in the part—three days' worth of work? For sure! I have to tell you, this crew and this cast are hilarious."