Jimmy Fallon was involved in a bar fight Thursday night in New York City while partying with friends and co-workers after taping "The Tonight Show."

Sources told the New York Post that Fallon and pals arrived at East Village bar Niagara around 10:30 p.m. and supposedly didn't get a warm welcome at what's described as a grungy rocker bar.

That's the problem right there. Everyone knows grungy rockers prefer Jay Leno when it comes to late-night television hosts.

Customer Ron Harrell wrote on Twitter, "Fallon just got in a fight at Niagara Bar. Go NYC." He posted a photo showing the suit-and-tie-clad Fallon being apparently comforted by a woman and guarded by a large glowering guy in an FDNY sweatshirt as a crowd gathered around.

One source told the Post, "There was some hostility from some people at the bar. Jimmy was not the aggressor, but he was caught up in it. It was broken up and Jimmy and his friends immediately left."

Late night hosts aren't what they used to be. Johnny Carson would have used Karate to clear the room, then sat down to finish his glass of whiskey.

Another source reportedly said, "There was a kerfuffle, a dust-up amongst other patrons. Jimmy was caught up in it, but was not hurt and turned around and left. It was not caused by him and he was in and out in five minutes."

Kerfuffle? Since when do grungy rockers say "kerfuffle?"

Fallon was back at work the next day, hosting Nicolas Cage, Emily VanCamp and a performance from Kiss.

Fallon, who became a dad last year, is known to go out after work, and seems to be popular at bars, including Bill's in Midtown, where he was recently spotted singing "You've Lost That Loving Feeling" along with other numbers.

The owners of Niagara have not commented on the "kerfuffle." Nor have reps for Fallon and officials from NBC.

Contact Tony Hicks at Facebook.com/BayAreaNewsGroup.TonyHicks or Twitter.com/insertfoot.