Z-axis glitch

The Z-Axis Glitch was a glitch in Super Smash Bros. Ultimate that was discovered in version 3.0.0, allowing every character to face the Z-Axis by exploiting the behavior of springs. It is easiest to perform in Stage Builder, but can also be done on Palutena's Temple, or by the use of Sonic's Spring Jump or Mega Man's Rush Coil. It was originally patched out in version 4.0.0; however, a new method involving was discovered in version 8.1.0. This method was later patched in 12.0.0.

Original method
In order to perform this glitch, the player needs to attempt to perform a wall cling the instant they start moving downwards after bouncing off a spring. The easiest way to do this is by making a custom stage with a wall right next to a spring. By attempting to wall cling after bouncing on the spring, the character will instead face forward, with their hitboxes following suit. Using the character to grab any character within range will cause them to face forward as well.

8.1.0 method
From version 8.1.0 onward, the glitch can be performed by Link using Ancient Bow and Arrow while the opponent is flinching by any Assist Trophy or Poké Ball Pokémon with a multi-hit attack (with the two most common ways being the use of Knuckle Joe or Fennekin), or a Smart Bomb. Upon successfully connecting Ancient Bow and Arrow with an opponent, the glitch is triggered. The behaviors and effects of the glitch are otherwise the same as the original method. Due to this, it is generally recommended that the player pause the game if the one is attempting to perform the glitch with Assist Trophies or Pokémon on Training Mode (which makes all characters intangible) until the helper in question disappears, since getting hit by another attack automatically fixes the glitch.

Results
Performing the glitch with various characters leads to various, interesting results:
 * Neutral special projectiles do not travel forward and into the Z-axis, instead staying in place.
 * Certain attacks will have the horizontal component of their knockback removed, with hitstun remaining the same.
 * The player is not able to move at all on the ground, as pressing down results in crouching. They must jump and move in the air instead.
 * The glitch can be fixed by grabbing a ledge, wall clinging again, or getting hit by an attack.
 * Most side specials and forward tilts will automatically fix the glitch (although some like Heel Slide will not), though forward smashes and forward aerials can be performed normally.
 * Back aerials, however, are impossible to perform (with the exception of and, who can perform their back aerials' angled variants).
 * Missing a grab or performing a grab release with causes the game to crash. Throwing the grabbed character does nothing, though the Pikmin will fly across the stage, before returning to Olimar.
 * In a 1-on-1 fight,, , , and will automatically fix themselves, due to their "facing the opponent" mechanic.
 * 's model faces the screen, though it keeps the normal Y-axis flattening.
 * If Mr. Game & Watch uses a move that makes him resemble the various Game & Watch characters from their original games (such as Chef or his down smash), they will be barely visible, due to them truly being flat, unlike Mr. Game & Watch himself.
 * This reveals that Mr. Game & Watch's model does not stand in perfect profile while facing the normal direction, although the flattening makes it appear as though he does.
 * Using Octopus will cause him to remain in the form until he moves beyond the blast zones.
 * Luma will spin in place while Rosalina remains on the ground, until usage of Luma Shot, which will cause Luma to face forward.
 * Performing a pseudo-crawl will cause the character to slide to the right, rather than staying in place.
 * Shippu Jinraikyaku yields the same result, though it, along with Shin Shoryuken, will altogether miss.
 * Cutscene Final Smashes will, like grabbing, cause any character caught to face forward.
 * 's grab sprite lays flat on the X-axis rather than the Y-axis.