NEW YORK – When is too much just the right amount?

Comedy Central hopes it has the winning number for “Night of Too Many Stars: An Overbooked Concert for Autism Education.”

The network’s third such biennial benefit, this too-fer is also a two-fer, originating from two coasts, and prerecorded as well as live.

Airing at 9 tonight, the broadcast will consist of a gala concert taped earlier this month at New York’s Beacon Theatre, along with live cut-ins from Los Angeles, where a star-studded phone bank will receive viewers’ contributions during the show.

George Clooney, Tom Hanks, Betty White, Conan O’Brien, Jimmy Kimmel, Bryan Cranston, Lauren Graham, Jim Parsons, Sofia Vergara and Weird Al Yankovic are among the celebrities booked to take calls in Los Angeles from donors.

Jon Stewart will be the host.

Meanwhile, the New York shindig will boast names such as Steve Carell, Stephen Colbert, Tina Fey, Sarah Silverman, Jimmy Fallon, Tracy Morgan, Joel McHale, Jim Gaffigan, John Oliver, Ricky Gervais, Lewis Black, Chris Rock and Triumph the Insult Comic Dog. Surely way too many!

“Night of Too Many Stars” comes packed with laughs, of course. But its underlying purpose is no joke, as Stewart wastes no time reminding everyone.

After greeting the audience with a bedbug joke, he turns serious, stating that one of every 110 kids is diagnosed as autistic.

“Tonight isn’t about curing autism or fighting it,” he says. “Tonight is about helping people that live with it now.”

And on with the show!

Among the night’s silliness:

•Colbert and Carell headline a song-and-dance number (including sexy flight attendants and someone in a goose costume) that pays tribute to heroic U.S. Airways pilot “Sully” Sullenberger.

•Morgan and Rock eviscerate the tender ballad “Scarborough Fair” until its writer, Paul Simon, arrives to straighten them out.

•And Silverman, in her comic persona as the world’s most winsome narcissist, accepts the self-created Legends of Autism Award, rejecting such candidates as former United Nations Secretary-General Kofi Annan and former President Jimmy Carter.

“I wish they could give FIVE of these away,” she says, breathlessly clutching her trophy, “so EACH of my bathrooms could have one.”

A few hours before the Oct. 2 taping, Silverman displayed a much different offstage manner – sweet and unpretentious – amid the bustle of a final run-through.

“I love this stuff,” she said, looking around her in the Beacon auditorium. “I came to rehearsal yesterday, and when I was done I just stayed the rest of the night! I’d so much rather be with other comics than go back to my hotel and watch ‘Law & Order,’ which is my second favorite thing to do. This is superfun.”

Plus, it’s for a worthy cause.

In truth, Silverman’s involvement was inspired by comedy performer-writer Robert Smigel, whose 12-year-old son, Daniel, is autistic.

“Night of Too Many Stars” arose from the difficulty Daniel’s parents had in finding him the right educational resources.

A few years ago, they joined with other parents to start their own school in New York. It required fundraising efforts. So did other educational programs nationwide.

Smigel, perhaps best known for his wisecracking canine hand puppet, Triumph, is held in great affection among the hip comic mafia. He got increasing support from fellow entertainers – and from Stewart early on.

“He has shepherded this whole thing,” Smigel said. “It’s not like it would happen and get the same attention if I didn’t have one of the superstars of comedy at the helm of it.”

“It’s a great charity, and it’ll be fun,” said Oliver, the crisply proper British correspondent for Stewart’s “The Daily Show,” during a rehearsal break.

“And I live around the corner, so it couldn’t be easier. It literally could not be easier.” Deadpan, he continued, milking the moment. “This is the least effort I could make this evening. It’s easier for me to do this than do anything else!”

Helping make it so easy: his authoritative British accent.

“A British accent can still extract money from Americans,” Oliver noted. “I’ll say, ‘Give me more money,’ and viewers will cast their mind back 300 years and obey.”

Odds are, they’ll laugh, too.