From PEOPLE Magazine Click to enlarge
Imagine you're an actress who has been told to gain 20 lbs. for your next role. Or that you'll be playing the mother of someone only eight years younger than you. These are the challenges Selma Blair, 36, and Molly Shannon, 44, face for their new NBC sitcom, Kath & Kim—but as they discussed with PEOPLE's Amy Elisa Keith, getting to eat junk food and wear thong leotards has been "so fun," Shannon says.

I read somewhere that you gained 20 lbs. for this role. Is that true?

SELMA: Yes. My character is not the kind of girl who works out, and she loves to munch. I'm eating a lot every scene—so I don't eat as big a lunch. [For more details, see box on next page.]

Is pigging out at craft services a welcome change?

SELMA: I can eat whatever I want on this show, as long as it's "funny food." Take that, Hollywood!

MOLLY: What's funny food?

SELMA: Colorful food. Candy, sweets, jelly beans.

MOLLY: And cinnamon rolls.

SELMA: Yeah, I've eaten a lot of those. It's good for my diet, because I OD on junk food and then want nothing but salads and chicken!

MOLLY: My character doesn't have to munch a lot, thank goodness. She's a fitness freak. She thinks she looks so hot.

Even in that thong leotard?

SELMA: She looks like a hot mama in that!

MOLLY: It's fun to put on the hair, nails and the short skirts. But goodness—I've gone to get coffee on the lot, and people think I've cut and colored my hair. And that I'd really wear a pink visor!

Can you believe you're playing Selma's mother? You're not that much older than she is!

MOLLY: [laughs] I would have been 8 when I gave birth to her! But it's not a big deal.

But is it a big deal to wear such revealing costumes?

SELMA: I wear a lot of underwear as my wardrobe. I'm like, "Really, are these underpants?"

MOLLY: Yup, it's all hanging out!

SELMA: But I'm past the self-consciousness. And I think Molly has the legs for all her short outfits.

MOLLY: I'm a runner, so these legs are all I've got.

SELMA: Once, during a break, she was running. And my manager comes on set and says, "Don't you think we should get you a trainer to come during lunch?" And I was like, "Oh, no, no, once you're in costume, you just can't do a thing." Then you see Molly jogging around all cheery in her hair and makeup, like, "I'm going for my jog." I was about to cry.

MOLLY: Because he wanted to get you jogging?

SELMA: I was totally busted. I thought I had an excuse [not to work out]!

MOLLY: In all honesty, it makes me feel more relaxed to go for a 25-minute jog.

SELMA: For me it's like, "What's the point?" I'll just stay soft. I'll go back to my trainers after this is over!