A good roast is practically irresistible: Everyone loves seeing a famous person teased mercilessly by equally famous peers. A bad roast, on the other hand, can be a cringe-fest, as the guest of honor bristles at an evening of poorly written jabs. These five roasts are the bottom of the barrel -- the times where "funny and mean" turned to "sad and awkward" almost immediately.

1. Justin Bieber

"The Comedy Central Roast of Justin Bieber" is painful to watch, mostly because it feels like a rich kid's birthday party where his parents have paid people to pretend they like him for a day. The roast was filled with an odd mix of celebrities (Martha Stewart, Snoop Dogg, Shaq) and celebrity hopefuls (Chris D'Elia, Pete Davidson, Jeff Ross) who mostly spent the evening making height jokes about roastmaster Kevin Hart.

While the jabs pointed at Bieber didn't hold anything back, the Biebs himself ruined the evening by closing with a speech that made it clear the event was a PR stunt ineptly designed to win back the public's favor after months of highly publicized bad behavior. As Bieber intoned, "This was a moment for me to show people where I am at in my life right now. Right now I'm in a moment of change. As I said, I've done a lot of things I'm not proud of, but we're turning a new leaf here," the night became even less fun -- exposed as a poorly thought-out stop on his apology tour.

2. Pamela Anderson

Comedy Central roast, believe it or not, was a charity event: The evening raised money for People for the Ethical Treatment of Animals (PETA), which was perhaps the only positive outcome of the whole night. It wasn't just that the jokes retreaded the same territory over and over -- half of them were about her appearance, the other half about her sex tape -- it's that the roast was nearly unwatchable thanks to Courtney Love, who spent the entire time intoxicated and writhing in her chair, pausing only to incoherently argue with her co-roasters or flash the audience. Despite all that, seeing the late Bea Arthur read aloud from Anderson's autobiography remains a must-see clip to this day.

3. Chevy Chase

The best comedy roasts have one thing in common -- a shared fondness for the person being roasted. That's what's fun about them: When Rob Reiner got roasted, it was obvious that everyone in the room actually loved him. The Friars Club roast of Chevy Chase, however, is cringe-inducing thanks to the obvious lack of respect from his peers. The most common joke topic of the night was Chase's former drug addiction, and watching him squirm, and sometimes openly heckle, the presenters bordered on the tragic. Whether it was that Chevy Chase wasn't "in on the joke," or that the jokes seemed unnecessarily cruel to a man in the twilight of his fading career, this roast is one to be avoided. And unlike Chase's film "Karate Dog," his roast was never even released to DVD.

4. David Hasselhoff

David Hasselhoff's roast is the polar opposite of Chevy Chase's -- where Chase acted like a schoolyard kid getting bullied, the Hoff basked in the attention, making sure he was the one laughing loudest at every joke. The result was almost as creepy: It's less fun for the audience when the person being roasted acts like they wrote all of the gags. Nonetheless, roasters Hulk Hogan, Jerry Springer, Lisa Lampanelli, and Whitney Cummings all took respectable shots in the Comedy Central event that ultimately amounted to new B-listers roasting an old B-lister.

5. Charlie Sheen

"The Comedy Central Roast of Charlie Sheen" took place at the height of Two and a Half Men" and went on a national tour to talk to crowds about his escapades with porn stars. While the roasters' jokes were dark, mean, and often hilarious (Jeff Ross's jab, "If you're winning, this must not be a child custody hearing" was particularly good), what made the roast rough overall was the overwhelming sense that the whole thing was enabling a man who was obviously in the midst of a personal crisis. As Sheen was proclaiming his own virtue, the public was watching him lose his TV role, custody of his children, and ultimately, his public relevance. Not that he minded: Despite the comics kicking him when he was down, at the end of the night, he still declared himself "winning."