That's tough!
Kate without exceptions, cause pudgy brits have my approval.... however...
Kate Middleton if it could be a Gay Pub called Rainbow McGee's, where Big Kate is known to give away shots of whiskey in exchange for sexual favors from any pretty bird who crosses her path. Oh, and she's always got a big bag of hula hoops to munch on. Use to keep it in her apron, but her paunchy belly crumbled the chips to dust!
But, Cameron Diaz if it's set in the mid 90's or early 2000's and she's going to school as a programmer, where, she meets an an even larger, nerdier friend named Jennifer Lopez. A meek, squeaky little butterball, also working at Tasty Freeze, with plans on starting her own video game company.
That was fun! Oh how about this?
This or that?
Three College Sophomores, sorority sisters, at a coffee shop, slowly transforming into PTA Moms with every sip of their hot cups of joe.
Or
A Little girl, randomly knocking on an apartment door of a macho guy in his early 20's, asking if he's seen her mommy. He's rude to her, slams the door, but doesn't realize she's a ghost about to curse him into a mommy!