(CNN) -- Comedian Jimmy Kimmel ripped into Jay Leno on his own show Thursday night, and Rosie O'Donnell -- who has been outspoken about her support of Conan O'Brien -- has canceled her January 27 appearance on "The Jay Leno Show."
"I'm a huge fan of Conan O'Brien," O'Donnell said Thursday while promoting her documentary, "A Family Is a Family Is a Family."
Instead of trying to get behind the big bus again, Leno should have passed "the keys to the new guy with the red hair, and not try to flatten his tires before he even gets going," she said.
Kimmel, who hosts "Jimmy Kimmel Live!" on ABC at 12:05 a.m., did his Tuesday show dressed as Leno, complete with prosthetic chin. Kimmel sat down for Leno's "10 on 10" segment Thursday, and cheerfully laid into the veteran late-night host.
When asked about the best prank he ever pulled, Kimmel responded, "I told a guy that five years from now I'm going to give him my show, but then when the five years came I gave it to him, and I took it back almost instantly. I think he works at Fox or something now." And these are just the latest celebrities throwing their two cents in during the 2010 late-night fight.
The Internet has been the most vocal supporter of Conan O'Brien. Although NBC has historically benefited from Leno's middle-America-type of appeal, viewer allegiance may be turning.
On Facebook, the group "Keep Conan O'Brien" -- using a profile picture of a graphic created by Los Angeles, California, artist Mike Mitchell with O'Brien in front of an American flag alongside the words, "I'm with Coco" -- has more than 11,000 fans. The groups "Save Conan O'Brien" and "We Support Conan O'Brien" each have more than 1,000 members.
On TVGuide.com, a poll with more than 5,000 votes as of this writing has also shown support for O'Brien, with 78 percent preferring to keep him on "The Tonight Show" at 11:35 p.m.
Doesn't anyone love Leno anymore?
Despite the blow-up on the Internet, said TVGuide.com's Mickey O'Connor, Leno still has his audience.
"There's a reason why his ratings were what they were," O'Connor said. "I hate to be condescending, but I think it's a generational thing. Conan's audience is much younger, and they're the audience that know about Facebook and Twitter. Leno's audience, while maybe larger, is older."
Nonetheless, "there's more ill will towards Leno now than there probably ever will be," O'Connor said. "He's such an innocuous character. He doesn't go out to nightclubs, he doesn't go out to openings, he's not political, he doesn't talk to the press. Right now, we probably have more information about Jay Leno than we ever have in the past."
For the viewers, perhaps, but for those who work within the entertainment industry, the view of Leno was a touch more cynical. One can trace the industry distaste back to 1992, when Leno first signed on to be the host of "The Tonight Show," said Mary Elizabeth Williams, Salon.com writer and culture critic for PRI's "The Takeaway."
"Leno had been a frequent guest on 'The Tonight Show,' a stand-up comic, and people thought he was really talented," Williams said. "And then, when he's up for 'The Tonight Show' seat and NBC decided he was safer than [David] Letterman -- who was always a gadfly and a rule-breaker -- they felt that he had sold his soul."
Comedian Patton Oswalt told a Los Angeles, California, radio station that Leno is "one of the best comedians of our generation," but that he "willfully shut the switch off" once he got on late-night, and "didn't do anything with [the show]." Comparing Leno to the guy he was up against for the "Tonight" seat, Oswalt said "the biggest difference between David Letterman and Jay Leno is, what kind of boss do you want?"
Leno, Oswalt said, is "the kind of boss that acts like everything is great and is always throwing parties for people, but is also passively aggressively kind of mean, and always doing weird, behind-the-scenes stuff." And then there's Letterman, he said, who's the kind of boss "who's like, 'I'm in a bad mood and I don't want to talk to you people,' but he doesn't play any games with you."
NBC seems confident that the online hits at Leno won't mean fewer eyeballs glued to their network at 11:35.
Dick Ebersol, chairman of NBC Universal Sports, told The New York Times that it is "chicken-hearted and gutless to blame a guy you couldn't beat in ratings" for O'Brien to fire shots at Leno during his monologues.
O'Brien's underdog status could be why he has built such an incredible fan base, Williams said. Those thousands of Facebook fans and Twitterers on #TeamConan likely weren't tuning in to his show -- otherwise, he would have had better ratings -- but they're standing behind the comedian now.
"We're all feeling this sense of, 'we're mad as hell,' " Williams said. "Conan is the embodiment of feeling screwed by the corporations. The fact that he's done it in a way that's funny and not polite and deferential ... we are all just really enjoying it. We all know what it feels like to have the brass ring taken away from us."
On the other side, she said, "you've got Leno, who's toed the line again and gotten rewarded for it. Once again, mediocrity gets the job."
Still, O'Connor said, only time will tell if all this passion over what becomes of NBC's late-night schedule will actually translate into ratings.
Right now, "people are voting for the better story, and I think it's how the story has been doled out by the respective networks," O'Connor said. "Take what they're releasing with a grain of salt; there's a lot more to the story that can't be public yet."