Eager to please, "Chuck" has delivered action, adventure, comedy and semi-romance.

What's been missing? Until now, there hasn't been a major shower fight scene involving a pop-culture figure.

In an episode scheduled tonight, that will change. Nicole Richie arrives to play the person who used to torment Chuck's sister Sarah in high school.

"Things go awry," producer Josh Schwartz promised. "The old high school shower becomes the location of a seriously wet showdown."

Zachary Levi, who stars as Chuck Bartowski, sums up the show:

"If you take 'The O.C.' and 'Die Hard' and 'Get Smart' and 'The Bourne Identity' and 'The Office' ... throw them all together and that's 'Chuck.' "

Schwartz is known for young romance, as producer of "The O.C." and "Gossip Girl." His college friend, Chris Fedak, came up with this detour, which they co-created and co-produce.

Chuck works at a Buy More store as a "Nerd Herd" techno guy. He has a sister (Sarah Lancaster) who thinks he should be ambitious and a friend (Josh Gomez) who doesn't.

In last season's opener, all of the CIA's secrets were accidentally imprinted in his brain before the computer crashed. Now he works with two spies, one scary and one sexy.

The latter is Sarah, played by Yvonne Strahovski. She "has to go back to her high school reunion, where she was not so popular nor nearly as beautiful," Schwartz says.

Her mission is to shadow an evil classmate. That leads to the shower scene. "They're attacking each other with pipes and plumbing," Schwartz says.

It took hours of filming and lots of choreography to get it right, Strahovski says. The bad part was that the water was cold; the good: "At least I didn't have to wear heels."

A casual observer would put his money on her. Richie is 5-foot-1 and Hollywood-thin; Strahovski is a tad over 5-9 and Aussie-strong.

She has Polish roots, but is a native of Australia. She landed the role only a few days after reaching the U.S.

Now she works in a symbol of Americana. Inside a Warner Bros. studio is a giant, fictitious Buy More store.

Levi says when he visited a Best Buy, he ended up signing autographs and posing for pictures with workers. They seemed fond of the show, despite its portrayal of them. "At the Buy More, you know, we're really a bunch of slackers."

Especially Morgan. "He's a good kid," Gomez says. "He's sweet-natured but ... he's not so goal-oriented."

Other characters have dismissed him as Chuck's "furry little friend." Gomez stands 5-foot-8, which isn't that little until he's near Strahovski or the 6-foot-4 Levi.

When the show started, Levi's character was kind of drifting, too. Schwartz blames "Chuck's college girlfriend ... the girl who broke his heart, who sort of sent him spiraling out of control."

She's coming back. She'll be in three episodes this season, played by Jordana Brewster.

That will let Chuck deal emotionally with his school-days angst. First, however, Sarah deals physically with hers.