The weirdness of roasts: Will the guest of honor laugh — or cry hard?

The truth hurts.

It also zings, stings, wounds, lambastes, cuts, slams, eviscerates and kills.

And it burns. That’s why they call it a roast.

The comedy roast is one of the oldest and one of the strangest and most unsettling traditions of show business.

I’m sure cavemen were roasting one another as soon as they discovered fire (ba-dum-bum,) but for nearly 70 years, dating back to the roasts at the New York Friars Club in the 1950s targeting Milton Berle, Humphrey Bogart, Sammy Davis Jr., Rocky Marciano, et al., the format of the showbiz roast has been pretty much the same:

You pay tribute to a popular figure from the world of entertainment (or sometimes politics or sports) by inviting a dais of longtime friends and colleagues — and the occasional What-the-bleep-is-HE-doing-here? guest — to take turns telling anything-goes jokes at the expense of the honoree. At the end of the night, the roastee gets to turn the tables on the roasters — and then everyone hugs and laughs and congratulates each other on being such good sports.

From 1974-1984, the “Dean Martin Celebrity Roast” specials were a staple on NBC. Check out the videos on YouTube and you’ll see legends such as Bob Hope, Ginger Rogers, Jack Benny, Lucille Ball, George Burns, Frank Sinatra, Don Rickles and Redd Foxx sporting period-piece outfits (enormous bowties on the men’s tuxes, ultra-bright colors for the women) cracking each other up with funny, sometimes cringe-inducing jabs.

Orson Welles, in a clip from 1978: “It’s always a pleasure to be back at one of these celebrity roasts of yours, where a gang of jolly, fun-loving people get together to use charm, wit and good humor, for one shining purpose: to destroy another human being.”

Comedy Central picked up the TV baton in the late 1990s, first airing the annual roasts at the Friars Club, and then, starting in 2003, producing specials once or twice a year, with Bob Saget, William Shatner, Joan Rivers, Flavor Flav and Pamela Anderson taking turns on the rotisserie.

I’m a fan of a good roasting, but it always makes me a little bit uncomfortable — and I’m just in the audience. Imagine what it must be like for the recipient of those zingers, which often delve into your career stumbles, your romantic heartbreaks, even family tragedies. Even as the target is laughing, you wonder if he’s thinking, That’s very funny, you bleeping bleeper. Now I know how you REALLY feel.

Of course, that’s the idea behind the roast, right? To make everyone in the room laugh AND squirm as the rich and famous take turns ripping each other in ways they’d never do on Twitter or even in a normal onstage appearance.

Everyone has Roast Immunity. You can say just about anything and the rule is: No hard feelings.

On Sunday, Comedy Central will air a roast of Bruce Willis, with Willis’ “Looper” co-star Joseph Gordon Levitt serving as roastmaster and the likes of Edward Norton, Kevin Pollak, Lil Rel Howery, “Moonlighting’s” Cybill Shepherd and even Willis’ ex-wife Demi Moore taking turns at the plate.

What we’ll see is an edited version of the three-hour roast, which was recorded July 15 at the Hollywood Palladium Theater. (Comedy Central edits the annual roasts for time and occasionally for content, e.g., when a roaster has second thoughts about a particularly offensive joke and asks for it to be removed.)

Vulture, USA TODAY, People and other sites have already posted a number of jokes from the evening. A sampling …

Gordon-Levitt: “Bruce Willis is what you get if you isolate the white part of Dwayne ‘The Rock’ Johnson.”

Cybill Shepherd: “On ‘Moonlighting,’ I played a former model, which I was, and Bruce played an a——, which he was.”

Demi Moore: “Our daughters are incredibly well-adjusted, considering two of them are half Bruce Willis. … Bruce considered the end of our marriage his biggest failure. Bruce, don’t be so hard on yourself, you had MUCH bigger failures: Planet Hollywood, ‘Hudson Hawk,’ campaigning for Michael Dukakis, turning down Clooney’s role in ‘Ocean’s 11’ so you focus on playing the harmonica…”

Per roast tradition, the panelists also aimed verbal darts at one another, with Kevin Pollak telling a devastatingly funny and wildly inappropriate joke about Edward Norton’s past with Courtney Love; Martha Stewart (who’s always a hit at celebrity roasts) zapping Lil Rel Howery; and Dom Irrera blasting Dennis Rodman, whose own attempt at a comedic monologue was reportedly a disaster.

Here’s hoping Comedy Central doesn’t edit out Rodman’s ramblings. Some clowns deserve to be roasted by their own ridiculousness.