It was about Bowser's Klawhopping technique in Brawl. For some reason, Bowser can cancel an aerial Flying Slam attempt into a jump just above the ground. It doesn't matter if you used up your second jump, either; you can do it as long as you're above a platform or stage.
It seems to force what's known as Infinite Second Jump Renewal (ISJR). In Brawl, if an aerial (or airdodge) finishes its animation exactly 1 frame before the character would land, that character can use their second jump, regardless of whether it's been used before. As long as you keep ending an aerial right before you land, you can continue to jump. Since the aerial has to be performed frame perfect (Brawl's generous buffer window means the jump doesn't, though) it's impractical, not to mention getting hit offstage while doing this means you're without a second jump to help you recover. Anyway, Bowser's Side-B seems to be cancelable into a jump in the same method as ISJR. You can Klaw to jump to Klaw to jump as much as you want. You can even sneak in a FAir if you do it right as you jump. Give it a try, it's fun.
There's another glitch involving Ganon that uses ISJR in a bizarre way. If you buffer both a jump and a Wizard's Foot out of an aerla right before you land, he does this weird flip thing and soars high in the sky, higher than he can reach with his jumps alone. It's more or less worthless competitively but amusing to see.
Bowser Demonstration Video
Ganon Demonstration Video
Can't find one for ISJR, maybe there's one with the technique labeled something else?