Adam Goldberg and Chris O'Donnell Adam Goldberg and Chris O'Donnell

On Wednesdays this fall, while CBS' CSI-ers and NBC's Law & Order keepers serve up justice with pensive, stone-faced seriousness, Fox will take a walk on the lighter side with Head Cases (premiering tonight at 9 pm/ET), an hour dramedy about an A-list lawyer about to go off the deep end, an "explosive disorder"-addled low-rent attorney who's already there and the halfway point at which they must meet to fight the good fights.

Playing the former — fallen hot shot and family man Jason Payne — is movie star Chris O'Donnell. Portraying Jason's unlikely new law partner, the outburst-prone Russell Shultz, is fellow film actor Adam Goldberg (A Beautiful Mind, Saving Private Ryan).

"I'd been taking a break [from movies] when this script kind of fell in my lap," says O'Donnell, who most recently completed roles in Kinsey and The Sisters. "I read it and loved it. It's a terrific character, plus I couldn't be more excited to work with the cast that's been put together."

And as a dad himself, O'Donnell likes taking on a commitment that doesn't yank him away from his own tykes. "I've got three kids, and my oldest is starting kindergarten, so the idea of being in one place was very appealing to me."

Filling out the Head Cases cast are Krista Allen (Unscripted, Confessions of a Dangerous Mind) and 9-year-old Jake Cherry, as Jason's estranged wife and adoring son, Rhea Seehorn (I'm with Her) as his loyal secretary and Rockmond Dunbar (doing double duty with a very different role on Prison Break) as his and Russell's therapist. Since the pilot was originally filmed, Rachael Leigh Cook ) exited the role of a mental-hospital acquaintance of Jason's and will instead go to Las Vegas this fall. ("She gave us a wonderful performance, but the character has simply been eliminated," explains executive producer Jeff Rake.) There's also been the late addition of Richard Kind (Mad About You), who will play the partners' ridiculously overqualified paralegal.

Part legal drama, part humorous "buddy pic," Head Cases has to mind the fine line between mining mental health for laughs and making it a politically incorrect mockery. "I think if anything, we might be making fun of normalcy," says Goldberg, rebuffing the potential perception that the show lampoons crazy people. "We actually might get a lot of letters and phone calls from normal society."

As series creator Bill Chais (The Practice) puts it, "We're not going to shy away from mental patients falling out of trees, which you'll see in the pilot; we just do it with sensitivity. It's all something that we take very seriously, something that we as a writing staff talk about and grapple with and consult with professionals about all the time.

"If we are irresponsible," he adds, "we want to make sure we are doing it properly."

Now that is just crazy.