If Betty White has taught us anything, it's that being old doesn't mean you're not hilarious. It also doesn't mean you're not really, really vulgar when the battlefield of comedy needs you to drop some serious F-bombs.

By entertainment standards, the roast -- a concept originated by the Friar's Club fraternity way back in 1907 -- is an absolute dinosaur. But it's like a T. rex that assaults you with politically incorrect character assassination and ridiculous celebrity humiliation instead of killer jaws and tiny arms -- old as it is, the roast walks the razor's edge of "too funny" and "too far." Here are five times the comics got that balance exactly right.

1. Charlie Sheen (2011)

"I respect Charlie Sheen, I do ... not his body of work ... it's all been very Christian Slater-ish ... he sucks, but he's good, but he sucks at the same time." And so it was that the late Patrice O'Neal immortalized Charlie Sheen at his own 2011 Comedy Central roast. The whole night was lightning in a weird bottle, mixed with tiger's blood and Twitter meltdowns, and shaken till it foamed over. "How do you roast a meltdown?," asked Jeff Ross. You do it just like this: A madman who set his own world afire giggles along as the sharpest comics in the industry point and laugh at the blaze.

As a bonus, this one helped put the brilliant Amy Schumer on the map. We'll take that.

2. Joan Rivers (2009)

The late, legendary Joan Rivers was made to be roasted on Comedy Central. She had the perfect combo of comedic icon status paired with plenty of ammo for her roasters, from her famously numerous plastic surgeries to her cringe-worthy red carpet interviews.

"Joan, I loved you in The Wrestler." With that intro, Whitney Cummings summed up what made Joan's roast the perfect dish -- the veteran comedienne's night in the chair not only cemented her well-earned relevance, it shined the world's spotlight on new talent. Even though most of that spotlight was focused on jokes about Joan's vagina.

3. Hugh Hefner (2001)

Hef's New York Friar's Club roast could've been a disaster. The nation was still reeling from 9/11, and the minefield of cliched old-man jokes just seemed too obvious. But thanks to the power of comics like Drew Carey and Sarah Silverman, it turned out to be the cream of the roast crop. Carey started out with a cathartic string of mega-profanity aimed at none other than Osama bin Laden, priming the audience for a combo of airhead-Playboy Bunny gags and old-age digs that moved at a clip and somehow managed to avoid any semblance of cliche. Silverman solidified the one-two punch with a short set centered on -- wait for it -- butthole waxing that was so left-field, it was clear she'd be a comedy queen by the time the roast ended.

4. William Shatner (2006)

Sometimes, it's the truth behind the jokes that makes a roast truly great. And it's that dose of reality that made Star Trek" co-stars like George Takei and Nichelle Nichols certainly had enough USS Enterprise drama to load their comedic cannons, completely apart from the former Captain's bizarre forays into spoken word albums and TV commercials. When Takei looks right at Bill and straight-up says, "Fuck you and the horse you rode in on" in that outrageous baritone of his, we laugh, because we know it comes from a place of truth. Feels good to let it all out, doesn't it, Mr. Sulu?

5. Donald Trump (2011)

We'll admit it. The thing that makes Donald Trump's Comedy Central roast so great is that it's a catharsis for the audience -- in 2011, we loved seeing the uber-rich, business tycoon get his just deserts, and in 2016, we love seeing it even more.

But it wasn't just seeing Trump get towered that made the night a standout -- it was the evening's completely unexpected roasters. A Marlee Matlin / Gilbert Gottfried double-team isn't something we knew we wanted till we got it, and Snoop Lion (aka Snoop Dogg) once again proved his comedic prowess with razor-sharp jabs like, "Donald says he wants to run for president and move on into the White House. Why not? It wouldn't be the first time he pushed a black family out of their home."

Enough said, Snoop. Enough said.