Robin Williams and Sarah Michelle Gellar star in “The Crazy Ones,” a new CBS comedy premiering tonight.

“The Michael J. Fox Show” 9 tonight, Fox

“The Crazy Ones” 9 tonight, CBS

From “Mom” to “Dads,” the fall season is loaded with new sitcoms about parents: No, it’s not just that every viewer has a parent somewhere. It’s also that there are a lot of older actors in Hollywood with pre approved likability.

Even when you’re talking about Robin Williams and Michael J. Fox, though, having a beloved mega-watt star at the top of your cast list won’t guarantee success for a new TV sitcom. Not in 2013.

Nope, you have to put them in great shows, and that’s just what NBC and CBS have done with these two comedy giants. It also helps to have a very strong ensemble cast, which both NBC’s “The Michael J. Fox Show” and CBS’ “The Crazy Ones” feature.

The former Reagan-worshiping Alex P. Keaton and the one time Orkan man-child Mork may play different kinds of dads in their respective shows. Fox plays local New York anchorman Mike Henry who, like the actor, has Parkinson’s. Also like the actor, Mike stepped away from his job after his diagnosis, but longs to be back in the saddle.

If Mike had trouble adjusting to being at home instead of out chasing hot stories, it was nothing compared to the adjustment his wife Anne (Betsy Brandt, “Breaking Bad”) and kids have been unable to make. The brood includes college flunk-out Ian (Conor Romero, “Rivers Wash Over Me”), Eve (Juliette Goglia, “That’s So Raven”) and Graham (Jack Gore, “We Are What We Are”).

Mike wants to get back to work without becoming a “human interest story” because of his illness. His boss Harris (Wendell Pierce, “Suits”) insists he’s just glad to have him back, but he’s not above seeing the human interest promotional angle in having a beloved news anchor back on the job and not letting his illness cramp his style.

The show was created by Sam Laybourne and Will Gluck and co-produced by Fox, who has said he wants the sitcom to be a realistic reflection of his own home life. There are “Parkinson’s moments,” of course, including a scene where he stumbles over a microphone cord trying to stop Eve from going off with his rival at the station, Susan Rodriguez-Jones (Anne Heche, “Save Me”). There are also moments intentionally written to disabuse anyone from feeling sorry for Mike. In other words, Mike is just Mike, and with Michael J. Fox playing him, he’s likable, human and just like any other well-meaning dad who screws up from time to time. The fact he has Parkinson’s quickly becomes just part of the character of Mike Henry, just as his job as a news anchor is.

In the second episode, for example, Mike goes upstairs to ask a new neighbor to lower the volume on the TV. He knocks at the door and a beautiful woman opens it. The whole episode is about Mike trying to downplay the fact he has an innocent crush on her, even though his wife is aware of the crush and rightly thinks it’s no big deal.

Then again, why wouldn’t Mike find the neighbor attractive? The actress playing her is Fox’s wife, Tracy Pollan.

“The Crazy Ones” takes its title from a 1997 Apple commercial called “Here’s to the Crazy Ones” that paid homage to great men and women who followed their own paths in life — Gandhi, Picasso, Bob Dylan, Amelia Earhart, John Lennon, Maria Callas and others. Of course, the title also fits any sitcom starring Robin Williams.

Making his return to series TV for the first time since “Mork and Mindy,” Williams plays Simon Roberts, a visionary ad agency executive whose eccentric style isn’t always in sync with the 21st century. Simon’s credo is leap first and a net will appear. Except when it doesn’t.

His daughter, Sydney (Sarah Michelle Gellar, “Ringer”) seems to be her father’s polar opposite, the practical one to his crazy one. But working together can perhaps change both of them, maybe bringing dad a little closer to solid ground and encouraging Sydney to allow her imagination to take flight.

The show, created by David E. Kelley, boasts a terrific ensemble cast, including James Wolk (“Mad Men”) as Zachary, whose overabundance of charm makes women swoon and is useful to the firm in winning new clients. Wolk almost steals the pilot episode, not once, but twice: First when he’s riffing with Simon when they are trying to get guest star Kelly Clarkson to agree to sing a jingle for McDonald’s, and later when he and Clarkson duet on a steamy version of “It Ain’t the Meat, It’s the Motion.”

But never underestimate another key ensemble cast member, Hamish Linklater (“The New Adventures of Old Christine”), the firm’s dopey art director. No one’s better than Linklater at showing astonishment that people are fundamentally nuts.

Williams says he’s sticking to the show’s script, which may be true, but he still manages to inject bits of his trademark out-of-nowhere riffs into the dialogue.

Neither show tries to re- invent the sitcom formula, but then again, why should they? They have great, always likable stars heading up solid ensemble casts in well-written and mostly plausible shows. Who could ask for anything more?