I just used 4 player battle(i control all of them), if player 2 and 4 crouches, player 3 can't move right(but can move left), but if player 3 moves right and player 2 crouches, player 4 can't crouch, and when player 4 crouches instead, player 2 can't crouch,
for example, (Player 1) is the target that (Player 3) wants to kidnap, but (Player 2) and (Player 4) Stops Him By Abusing This Glitch(But Wario Din't Walked Right), Then Player 1 Kills Wario
Sorry If I Made A Mistake, I'm Not Very Good At Grammar
I Hope You Understand Me, If No Then Ok
Works On All Characters On All Stages
It's Very Hard To Get It Work In Online Mode, Because Players Doesn't Crouch Too Much, And I'm Not Sure If It Works There, Let's Hope Not

if you don't think it's true, then try it, if it doesn't work for you, then it means it only works for me or something

My best guess is that your Keyboard simply cant handle all those different inputs simultaneously. This is just an assumption though, so Im propably wrong with this one.

Yeah, its a result of a cheap keyboard. Your keyboard is probably built exclusively for typing, so there's no need for several inputs to be used at once. Same on any keyboard in my school library.

*sigh* ok...