The "Tonight Show" is changing hosts again, this time, Jimmy Fallon is taking over for (mostly) long-time host Jay Leno, who will end his 22-year run as host of the show when Fallon takes over in spring 2014.

Leno congratulated his replacement at the beginning of his nightly monologue, while taking a shot at the NBC executive who are pushing him out.

"As part of the transition, 'The Tonight Show' will be returning to its original home in 30 Rock in New York" from Leno's base in Los Angeles, said NBC, in a statement.

Leno's contract is set to expire in 2014, so many industry observers had been expecting an announcement.

"I just have one request of Jimmy," Leno said. "We've all fought, kicked and scratched to get this network up to fifth place, okay?  Now we have to keep it there.

"Jimmy, don't let it slip into sixth," he continued. "We're counting on you."

There had been a lot of recent speculation that Leno may be leaving the Tonight show, and few are surprised that Fallon has been announced as his replacement. The two hosts had even started working the headlines about the possibility into their nightly routines.

Fallon downplayed the rumors, while Leno took swipes at NBC, comparing NBC executives to snakes, joking about the network's lagging ratings and called the shuffle of hosts NBC's version of March Madness.

Two days before the official announcement, Fallon and Leno did a parody of the song "Tonight" from the musical "West Side Story."

Prior to Leno's upcoming exit from the "Tonight Show," he had left in 2009, with Conan O'Brien, who was then the host of "Late Night," which Fallon now hosts, taking over "Tonight Show" hosting duties.

Leno moved to his own show, "The Jay Leno Show," in the fall of 2009. The move brought terrible ratings and NBC decided to move Leno back to the "Tonight Show" in 2010, leaving O'Brien unemployed.

O'Brien then moved to TBS to host his own show, "Conan," and the experience left O'Brien will bad feelings towards Leno and NBC.

"I want to congratulate Jimmy," said O'Brien during the monologue on his show. "That is a really fun gig."

Letterman, who was passed over for Leno in 1992 when he first took over for Johnny Carson, had more to say.

"NBC, God bless 'em, announced the official date for Jay Leno's departure, no mention of his official date of return, however," said Letterman.

He followed it up with a top 10 list of "things we'll miss about Jay Leno", including number four, "Can't remember the name of the bit, but it's the one where Jay is walking."

"Folks, I got to be honest with you, I had a really awkward day today," said Leno, himself addressing the situation with Letterman and the "Tonight Show." "I had to call David Letterman and tell him he didn't get the 'Tonight Show' again."

NBC is said to be concerned about losing younger viewers to ABC's Jimmy Kimmel, whose show, "Jimmy Kimmel Live" was moved to the same time slot as Leno and David Letterman's "Late Show," from its previous slot at midnight at the beginning of 2013 to compete with the other shows.

"The more time Jimmy Kimmel is in that slot, the more the young audience goes that way, the harder it is for [Fallon] to keep that audience," a source familiar with the network's thought process told the Hollywood Reporter.

Leno, 62, does what the New York Times called "Las Vegas-style comedy" while Fallon, 38, incorporates "a more contemporary and varied brand of entertainment," including use of social media.

"On behalf of all New Yorkers" state Governor Andrew Cuomo praised the move, saying that he's "pleased to welcome 'The Tonight Show' back to its first home."

When the "Tonight Show" began in 1954, the "original 'Tonight Show' ushered in the modern era of television," Cuomo said. "It is only fitting that as 'The Tonight Show returns to our state, it will be headlined by New York's own native son and resident, Jimmy Fallon."

Past "Tonight Show" hosts have included Steve Allen, Jack Paar, Johnny Carson, Leno and O'Brien.

Carson served as host for 30 years before Leno took over and is still held up as the model all others are compared to. Lorne Michaels, the producer of "Late Night," has called Fallon "the closest thing" this generation has to Carson.

"I want to thank everyone here at 'Late Night,' the staff, the crew and, of course, the Roots," Fallon said, during the taping of his show. "I have to say thanks to Jay Leno for being so gracious.

"It means so much to me to have his support," Fallon said. "I just want to thank the fans for staying up to 12:35 a.m. and for watching us."