Wall Clips
Helper Grab Wall Clips
When a helper is hanging from Kirby, the Helper's hitbox is disjointed from Kirby's hitbox, allowing for collision glitches.
Clipping through walls
Depending on the helper, Kirby will be able to pass through walls (Helper Hitboxes shows the specific hitboxes).
Chilly and Smirror helpers allow Kirby to clip through walls with no additional setup (holding forward to pass through).
Many helpers, such as Capsule J., require Kirby to enter the wall while facing the opposite direction you approach the wall from (so if Kirby is approaching the wall and moving right, they will need to be facing left).
Wheelie cannot clip through walls due to their hitbox. Plasma Wisp cannot hang from Kirby, so they cannot be used.
Clipping through the ground
Some helpers have a hitbox which allow them to clip into the ground by letting go of Kirby close to the ground.
Use of a second controller is required. Helpers grab onto Kirby by holding up, and let go by releasing up.
Going past mid-boss screen boundaries
In mid-boss battles, the screen stays in a fixed position.
If a helper is outside of the screen boundaries, they will be forced into the screen, regardless of what is in the way.
This can allow Helpers to clip into walls when positioned correctly.
In most cases, only Helpers can do this, though Kirby can use it in certain cases.
Clipping through walls using Wheelie
Method 1
If Wheelie is inside a wall, they can poke slightly out so Kirby can get on them and enter inside the wall.
In order to stay in the wall when hopping off Wheelie, Kirby will need to use a move that sends them in a direction quickly, such as Ninja Kick, etc.
An alternative to this is to open the pause menu when hopping off and selecting an ability, which will keep Kirby inside.
It is also possible to get into the wall this way by hovering, but it is difficult to do.
Method 2
Hopping on Wheelie stores Kirby's horizontal momentum. By hopping off Wheelie with enough horizontal speed in a pixel-perfect location, Kirby can clip through the ceiling from a corner.
First, Kirby needs to jump on Wheelie while starting a Wheel attack. When Kirby gets on Wheelie, this speed is stored.
Then, the pixel position needs to be lined up. It will depend on the wall.
Once in position, Wheelie needs to jump up towards the corner, followed by Kirby also jumping off. The stored momentum will cause Kirby to propel horizontally and through the wall.
A more detailed explanation can be found here (English translation pending).
Auto-scroller glitches
Jumping through screen ceiling boundary
Kirby is able to jump past the ceiling of a verticially scrolling autoscroller.
By hovering with the jet ability, Kirby can be pushed into the wall, as hovering with jet will always put Kirby back in-bounds if above the screen boundary.
This glitch is most commonly seen in the auto-scroller in Revenge of Meta Knight, Chapter 2.
Using a throw move to pass through walls
During an auto-scroller segment, Kirby can go through solid walls while performing a Jet Dive or Ninja Air Drop.
The throw can also pass through walls and slopes.
Ground clip using falling star blocks
In The Great Cave Offensive, Kirby can fall through the ground using falling star blocks in the Garden area.
If Kirby is standing where the star block lands, and Kirby cannot be hit, Kirby will clip inside the ground.
There are many methods, such as using a Stone transformation or by overlapping with an ability hat.
Ceiling clip through a 1 tile gap
This can only be performed by Bonkers or Buggzy helpers.
If either partner jumps into a 1-tile tall gap that is below a ceiling, they will clip through it.
They will be quickly shot upwards. If they fly off-screen, they can come back by hovering.
Helper Teleport Wall Clips
Biospark
If Kirby is grabbed by a Biospark enemy in an area with a low ceiling, a Helper can teleport to Kirby during this animation and appear inside the ceiling.
Tac
A helper needs to be captured by a Tac. If a Tac is killed inside a wall as it is flying away, the Helper that was captured will be inside the wall.
Reference Videos
0:00 - Helper grab wall clip through the ground
1:48 - Clipping through walls using Wheelie (Method 1)
Helper grab wall clip with Chilly
0:00 - Going past mid-boss screen boundaries
0:41 - Ground clip using falling star blocks
1:03 - Using a throw move to pass through walls
2:02 - Clipping through walls using Wheelie (Method 2)
2:46 - Ceiling clip through 1 tile gap
3:03 - Helper teleport wall clip using a Biospark enemy