Way back in 1999, Nintendo held a promotional event at the now-defunct MGM Grand Adventures Theme Park in Las Vegas. Called “Slamfest ‘99,” the event pitted Mario, Pikachu, Donkey Kong, and Yoshi against each other in a wrestling match to promote the upcoming N64 release of the original Super Smash Bros.
Unless you were actually present at the event, the only other way to see it was via a livestream through Nintendo's site. Zelda 64 Planet managed to take a few screenshots, with Vice publishing them online back in 2020, but the pictures weren't very good since livestreaming technology was pretty bad back in '99.
We do know that the event certainly took place thanks to descriptions appearing in various publications. Here's what Nintendorks had to say about the event: "Mario and Yoshi were on one team, Donkey Kong and Pikachu were on the other. It was quite funny to see the life-size mascots bouncing around a wrestling ring. Mario went on a crazed rampage hitting everyone in sight, and instead of Yoshi, Donkey Kong accidentally hit himself with his 'mallet of doom.'"
And here's how N64 Magazine described it: "Even the ref got in on the act, biting Pikachu’s ear and declaring that it tasted ‘like chicken’. Mario shocked us with his low blow antics and Kong knocked himself out with his own magic hammer, but they all wound up best of friends at the end, the match being declared an honorable draw."
Yes, the match ended in a draw. After minutes of each mascot pummeling the other, they all sort of just ran into the center of the ring and collided together, knocking them all out at once. A disappointing end, since Donkey Kong really should have taken this fight.
For the longest time, only grainy images of the event survived, but recently, actual photographs have been unearthed courtesy of Ed Espinoza (and with thanks to Eurogamer). These photos are way better and actually provide a bit of a play-by-play of the event, which is the best we'll get as no recording is known to exist. But then again, nobody knew these photos existed until just now, so who knows? Maybe there's a recording out there after all.