Scott D. Pierce: So Robin Williams acts like a 4-year-old?

Sarah Michelle Gellar is the mother of a 4-year-old daughter and a 17-month-old son she's raising with her husband, Freddie Prinze Jr.

On TV, she stars as Robin Williams' daughter in "The Crazy Ones." And the former helps her with the latter — or maybe it's the other way around.

"I'm not sure which way it works," Gellar said on the set of the CBS sitcom, which is filmed on the Fox backlot in Los Angeles. "Either Robin has made me a better parent, or being a parent has made me a better actor to work with Robin Williams.

"Because no matter what ridiculous thing my 4-year-old says or Robin says, I can keep a straight face now most of the time."

Robin Williams is Robin Williams. He'll always be the craziest of "The Crazy Ones," as you can see in the bloopers that air at the end of each episode (Thursdays, 8 p.m., Ch. 2).

But "The Crazy Ones" is not the show that many imagined when CBS picked it up. It's not all about Williams, and he doesn't overwhelm the show.

Williams stars as Simon Roberts, the rather unorthodox head of a top Chicago ad agency. He works with his daughter, Sydney (Gellar), who's his uptight opposite. The cast includes pretty-boy Zack (James Wolk); neurotic Andrew (Hamish Linklater); and smart-and-sexy assistant Lauren (Amanda Setton).

"I signed on because I thought I wasn't going to have to work that hard," Linklater joked. "I thought — this is his vehicle. Fantastic. I'll sit in the back. Maybe I'll stay home sometimes. But then it turned out to be a lot of work, actually."

"The Crazy Ones" quickly became an ensemble comedy. Williams spices things up pretty much every time he's on screen, but he's not the main course in every episode.

"Clearly, at the beginning, we all looked at this as a Robin Williams vehicle," said creator/executive producer David E. Kelly. "Once it was cast, we knew we had quite an ensemble here."

Which is just the way Williams likes it. He has high praise for all of his castmates, and he shot down the idea that he's improvising any more than "once in a while."

"It's really lovely," he said. "I love working with these guys."

And Williams admits he was sort of worried heading into his first TV series since "Mork & Mindy" went off the air 32 years ago.

"Because," he said, "after a while I'd go '[Expletive]! There's a[n expletive] load of work, Daddy! Well, you young people, go take a line.' "

Of course, the set of the fictional ad agency features an enormous, somewhat impressionistic painting of Williams. It has to be 30 feet tall.

"It's like being on drugs again," Williams said. "It's very surreal.... The first day I walked on the set and went, 'Oh, OK, no pressure.' "

Scott D. Pierce covers television for The Salt Lake Tribune. Email him at spierce@sltrib.com; follow him on Twitter @ScottDPierce.