Denise Richards is having a ball on the set of 90210.

On September 26, the 41-year-old actress began filming her guest appearance for the CW series' 100th episode. Wearing a tight teal pencil dress, the tanned star watched series regulars AnnaLynne McCord, 25, Jessica Stroup, 25, Shenae Grimes, 22, and Jessica Lowndes, 23, participated in a powder puff football game.

When one Twitter user called Richards "old" and asked if she'd be playing a "great grandma on 90210," the single mother-of-three sarcastically replied, "Yes, I play the great great grandma, smarty pants." All jokes aside, Richards plays a West Beverly High School alum turned wealthy socialite who runs an exclusive women's club that Naomi Clark (McCord) desperately wants to join.

PHOTOS: 90210 stars' best red carpet moments

During the outdoor shoot in Manhattan Beach, California, 90210's Matt Lanter, 29, Michael Steger, 32, and Josh Zuckerman, 27, wore blue and white cheerleading uniforms as they revved up the crowd from the sidelines.

"Today I was dressed as woman, dealt with disgruntled Matt Lanter, humiliated by Tristan Wilds and supported by Josh Zuckerman," Steger tweeted. "All in a day's work."

VIDEO: Shenae tells Us why she doesn't relate to her 90210 character

Richards isn't the only A-lister appearing on 90210 this season: "Call Me Maybe" singer Carly Rae Jepsen, 26, performs in the premiere episode, and five-time Olympic gold medalist Ryan Lochte, 28, will make a cameo on the show October 29. Richards' episode airs November 26.

The fifth season of 90210 premieres October 8 at 8 p.m. EST on The CW.

This article originally appeared on Denise Richards Joins 90210 Cast for Powder Puff Football Game