Credit: GSI Media

The leading ladies of 90210 are known for their tiny frames, and Gillian Zinser is no exception.

"I guess I'm just built this way," the svelte 26-year-old told Us Weekly at 2nd Annual Hollywood Rush Benefiting the Baby Dragon Fund in L.A. Sunday. "I'd love to put on a few pounds, so I hang out by the doughnuts [at craft service], but it hasn't hit yet."

Zinser joined The CW hit in 2009 as surfer chick Ivy Sullivan; she was promoted to series regular in February 2010.

"It's a fun set and we're all close in age and spirit," Zinser said of costars AnnaLynne McCord, 24, Shenae Grimes, 22, Jessica Stroup, 25, Jessica Lowndes, 23, Matt Lanter, 28, Tristan Wilds, 22, and Michael Steger, 31.

"There's a lot that goes on behind the scenes. In fact, we always joke that it would make a really great reality show to show the behind the scenes on 90210," Zinser told Us. "What goes on in hair and makeup is far more entertaining that a lot of what's out there!"

"The whole cast is a bunch of pranksters," Zinser added. "We're always laughing."