update on this,
few more of kirby's copy ability ( , , and ) can also cause the glitch.

Also

Any copy ability that makes his hat become part of his sprite works.

No.

among others don't freeze.

not necessarily
megaman hat is part of kirby's sprite when he uses buster, but the game didn't freeze.

Oh.
I hadn't finished testing which copy abilities froze the game and which ones didn't when I made that post, and I just assumed that it was related to the hats (which wouldn't make any sense). I finished testing, and it seems to be related to if an ability can be land-cancelled or not; abilities that cannot be land-cancelled (aside from 's for some reason) freeze the game.

Am I the only one who's Hyrule Castle is kinda...broken?
Whenever I have a match on that stage it starts off well but eventually it'll freeze every so often, and the constantly changing frame rate results in the music becoming ear rape
I doubt it's an issue with my computer as all the other stages work perfectly fine, and my friend has the same issue too
Don't know whether it'll show up online or not, as I've only tested it offline with CPUs

Yoshi's Island or Yoshi/s Island

If as you are able to get bowser right next to you and spam your normal attacks he'll be stuck there untel you stop...

i can run hyrule castle without problem.
maybe the game hates you and your friend?

three letters
SDI

The fan item may able to juggle some enemies infinitely such as Issac. I tested it on high level CPUs and with a buddy and DI didn't work.

I was fiddling around with turbo mode, and found out that 's Dash attack and U-Smash loop for some time if cancelled.
See for yourself in the replay below.

[Click to see attachment]

You can't grab airborne items that aren't turnips or pac-man's fruit

Also Kirby can't inhale items

SDI