Jay and Dave together? Could it be true?

It is, and there they were, Jay Leno and David Letterman sitting on a couch – with Oprah Winfrey between them — upstairs at the Ed Sullivan Theater, where Mr. Letterman tapes his show.

The spot was shot last Tuesday afternoon, under the strictest of secrecy which involved both Mr. Leno and Ms. Winfrey flying in surreptitiously to New York, and arriving incognito at the theater, while Mr. Letterman was in the midst of taping his show for that night. It also involved Jay wearing a disguise: hooded sweatshirt, glasses and faux mustache. If you happened to be on Broadway between 53rd and 54th street last Tuesday about 4:15, you might have seen a man fitting that description slip into the theater by a small entrance under the marquee.

According to staff members of the “Late Show with David Letterman” who were on the scene that day — including the executive producer, Rob Burnett – it all happened because Mr. Letterman had an idea he thought would be truly funny: a Super Bowl ad that featured the two longest-running adversaries in late night, sitting with Ms. Winfrey as though at a Super Bowl party.

What gave the idea extra spin, of course, was that the relationship between Mr. Letterman and Mr. Leno has been especially fractious of late in the wake of NBC’s moves that led to the departure of Conan O’Brien from the “Tonight” show and Mr. Leno’s impending return to the show, where he will once again go head to head with Mr. Letterman.

In the weeks since the decision was announced, Mr. Letterman had been notably acerbic in his on-air jokes about Mr. Leno, suggesting he was a schemer in some way in the moves that led to the changes in late night, and Mr. Leno had responded with jokes about Mr. Letterman’s well-covered romantic entanglements.

That added to the surprise viewers encountered when the ad came up and there the two comics were, flanking Ms. Winfrey, in essence for a promotion for Mr. Letterman’s show.

As Mr. Burnett described it, Mr. Letterman had the idea to invite Mr. Leno to participate, playing off a similar ad he put together with Ms. Winfrey the last time CBS had the Super Bowl, in 2007. “Dave wrote the bit himself,” Mr. Burnett said. “He just thought: it’s the Super Bowl, you’re supposed to entertain people.”

Steps were taken to contact Ms. Winfrey, who agreed immediately, Mr. Burnett said, and then Mr. Leno. Mr. Burnett said he spoke with Mr. Leno’s executive producer, Debbie Vickers. “She asked if this was for real and then she laughed for about 10 minutes,” Mr. Burnett said.

Mr. Leno quickly agreed, but the idea had to be passed by the top NBC executives, including the chief executive, Jeff Zucker. Permission was granted.

Mr. Leno was able to get Tuesday free – NBC had rearranged its schedule to pre-empt his 10 p.m. show that night — and took the NBC corporate jet, Mr. Burnett said. There seemed little chance though that Mr. Leno could sneak into Mr. Letterman’s theater unseen, so the idea was hatched to try to sneak him in during a live taping, in disguise.

Both guests turned up while Mr. Letterman was on stage doing his show. They were kept in a secret green room until the show was over and the theater was cleared. Then Mr. Leno and Ms. Winfrey went up to the theater balcony where a living room set was fashioned with a faux TV and a couch.

Mr. Letterman arrived a short time later. The two late-night rivals greeted each other warmly, Mr. Burnett said. “It was very friendly, very professional, totally cordial,” he said. “You could tell these were two guys who have known each other for a long time.”

The idea Mr. Letterman came up with was for him to be first seen alone, complaining about being at the worst Super Bowl party ever — then to be seen in a two-shot with Ms. Winfrey as he had been in 2007, with her telling him to be nice. And then Mr. Leno would be revealed at the other end of the couch saying that Mr. Letterman was only complaining because he was there.

Mr. Letterman followed doing a mock-Jay voice. The 15-second spot was shot quickly and efficiently, Mr. Burnett said. “I’d say it took no more that 20 or 30 minutes,” he said.

“I think everybody wanted to do it just because they all knew it would get attention and they all just wanted to do something funny.”

After the taping was completed, Mr. Letterman thanked his guests and they said a cordial goodbye, Mr. Burnett said. The two stars slipped back out into the Manhattan night, Mr. Leno back in his faux mustache.

“This wasn’t done to help Dave or to help Jay,” Mr. Burnett said, “though I think it does help both of them. It was just done because Dave thought it would be funny and would entertain people. Nothing went beyond that.”