The fall television season kicked off in the last week of September with CBS' Robin Williams sitcom The Crazy Ones bringing in 15.5 million viewers in Nielsen ratings for the week ending Sept. 29, towered over a special 9 p.m. ET/PT airing of NBC's Michael J. Fox Show at 7.5 million.

On a list of the top 20 shows this week, The Crazy Ones came in at No.6 with its series premiere episode. The newcomer was about to reign over veterans such as The Voice (in its fifth season), Dancing with the Stars (in its 17th season) and Modern Family (in its fifth season). No. 1 on the list was the NFL game, New England Patriots vs. Atlanta Falcons. The NBC airing racked in 20.5 million viewers.

The Crazy Ones is a workplace comedy about an advertising salesman whose unorthodox methods and behavior would get him fired, were he not his own boss. Simon Roberts (Williams) heads an agency representing some of the biggestbrands in the world. His business partner is his daughter Sydney (Sarah Michelle Gellar) are the two are exact opposites. She is focused, organized and eager to make a name for herself, but also too busy parenting her father," according to CBS' official synopsis of the show. They have a talented, hard-working and neurotic team with them as they try to take over the advertising world.

Gellar called her latest role on The Crazy Ones the "most fun" she has had on set.

"It's amazing. I've been in this business for 33 years and it's the most fun I've ever had," she told CBSNews.com about the show. "I'm learning something new every day. I smile. I laugh. I have the nicest co-stars. Robin Williams -- honestly if I went on and gushed about him even more you would probably think I made him up. He's the kindest, most generous [person] and he's so grateful for the position that he's in. He cares about my children and their birthdays and what I'm doing. It's a real family show for us."

Gellar starred in Buffy the Vampire Slayer and All My Children, and also hit the big screen in such films as I Know What You Did Last Summer.

The Crazy Ones airs Thursdays at 9 p.m. ET.

Tags: The Crazy Ones CBS