Zombie Glitch allows you to take unlimited hits from all sources except for pits which will instant kill regardless.

During the zombie state, checkpoints can still be activated. Collecting a coin breaks the zombie state but restores the player to full health. Music will be broken after the death sound effect is played, but other sound effects will still happen.

Clip of glitch being discovered:

The glitch can be performed by pausing roughly half a second before receiving damage while already hurt. If timed too late, the player will reset to the last checkpoint, but if timed too early, the normal death animation will play. If no death animation plays and the player is labeled 'Dead', the glitch is now active.

Upon finishing a level during the zombie state, the game will complete the level normally. However, once all the lives are removed to add to the score, the game will send the player back to the start, and enable practice mode.

Despite this, the next level is still unlocked and the level is counted as complete, even in this state. Proof with save info deleted beforehand:

This glitch will be useful for later levels in the run where waiting on enemy cycles is more constant, but likely not for Area A.