Image caption Gellar plays Williams' daughter in the Chicago-set sitcom

Robin Williams is returning to TV screens for the first time since starring in the 1970s show Mork & Mindy with a new comedy, The Crazy Ones.

Williams, 62, who rose to fame as the alien Mork in the hit series, will play an eccentric advertising agency boss in the sitcom.

Buffy the Vampire Slayer's Sarah Michelle Gellar will play his daughter.

The show, from Ally McBeal creator David E Kelley, is due to air in the US in September.

Williams said he hopes audiences will be drawn to his character, Simon Roberts, and will enjoy watching how he relates to his daughter.

"You have to establish a character that people buy into," he said.

"I think people will buy into not just my character but the relationship with everybody else. He has good ideas and bad ones."

Williams, who was known for his improvisation skills in Mork & Mindy, will be given the freedom to ad lib and be spontaneous in The Crazy Ones.

"He says my words perfectly. Then he uses his," said Kelley.

"He manages inside the box, then we give him a few takes where he gets to take out of it."

The show is one of a number of new shows added to the autumn TV line-up in the US.

A new four-hour mini-series on NBC will see Diane Lane in the role of former first lady and US Secretary of State, Hillary Clinton.

NBC said the show, simply named Hillary, will track Clinton's life and career from 1998 to the present.

The series will air ahead of the 2016 US presidential election.

Clinton has not said whether she will make another run for the Democratic nomination for president.