Jimmy Fallon, Justin Timberlake deliver hilarious star-studded 'Saturday Night Live' episode to end the year, includes Madonna

The duo brought on the laughs with a celebrity guest lineup that also included Paul McCartney, Barry Gibb and Mayor Bloomberg.

Justin Timberlake (second from left) and Jimmy Fallon perform ‘Wrappinville’ during an ‘SNL’ sketch.

"Saturday Night Live" ended the year with a bang and a whole lot of laughter with Jimmy Fallon hosting, and Justin Timberlake as co-host and musical guest.

The hilarious episode included some of the year's funniest skits, as well as a star-studded lineup of celebrity guests.

Fallon's opening monologue was supposed to be an act with the late-night talk show host's musical idols David Bowie, Bob Dylan and Paul McCartney, but it began with him on stage alone.

Paul McCartney (left) dueted with Jimmy Fallon on Saturday’s episode of ‘Saturday Night Live.’

"Unfortunately they can't be here," he explained to the audience. "Traffic is tough at this time of year and all of them are currently stuck in the Lincoln Tunnel."

But because "the show must go on," Fallon started strumming his guitar and singing "Joy to the World," with impersonations of Dylan, Bowie and McCartney. Before he could finish, the former Beatles singer arrived to help him with the musical performance.

Madonna (left) joins Justin Timberlake (center) and Jimmy Fallon during a sketch on ‘SNL.’

"Paul, I thought you were stuck in traffic?" Fallon asked.

"I was, but then I took a Citi Bike," McCartney explained.

The men sang "Have Yourself a Merry Little Christmas" to the approval of a roaring audience.

Justin Timberlake (left) and Jimmy Fallon (right), along with Madonna and Barry Gibb, on ‘The Barry Giff Talk Show.’

The sketch comedy show also included a funny skit with Fallon and Timberlake dressed as Christmas presents while performing a rap medley about wrapping gifts.

Another offered a role reversal as Timberlake impersonated Fallon, who was a guest on celebrity "Family Feud" with the NBC team competing against CBS. Fallon played "Big Bang Theory's" Jim Parsons on the CBS side.

Jimmy Fallon raps a verse in ‘(Do It on My) Twin Bed’ on ‘Saturday Night Live.’

"So great, so great," Timberlake repeatedly said in an attempt to portray the next host of the "Tonight Show."

The funny pair hosted a segment of the "Barry Gibb Talk Show," which included Madonna as a guest who spoke about unity among politicians before putting her blinged-out grill on her teeth. It was the first time bringing back the skit since Robin Gibb's passing in 2012.

Left to right: Michael Bloomberg, Jimmy Fallon and Seth Meyers on ‘Weekend Update’ on ‘Saturday Night Live.’

As the duo ended the sketch with a song, they were surprised by Barry Gibb himself who joined them for the tune.

One of the funniest musical performances of the evening was the song "(Do It On My) Twin Bed." The ladies of "SNL" belted out the ballad about sleeping with their boyfriend in their childhood bedroom while visiting their parents over the holidays.

Fallon had a rap in the song that included lyrics like: "Girl you know I love you but let's be clear / I've got lots of trouble getting horny here."

Other highlights included New York Mayor Michael Bloomberg joining Fallon and Seth Meyers for an episode of "Weekend Update" and when Timberlake lit up the stage with his laser light show performance of "Only When I Walk Away."