Zombie

Zombie refers to the state when you have negative health but didn't die. This state notably makes Crash invulnerable to most things. Getting Zombie on NTSC-U 1.0 will crash the game.

History
In 2014 BetaM and Pull found a way to skip Dingodile for 100% using Zombie. In 2018 while playing with Camera Glitch, Bandicraft shows you can give Cortex Zombie

Effects
While in Zombie, Crash can't take damage but can die to certain things. Zombie Crash can get world checkpoints as usual but can't get normal checkpoints. Getting in range of getting a normal checkpoint will lock it, you can't get it after losing Zombie until you die. Some camera triggers don't work correctly. Some enemies won't track Crash.

Obtaining and losing Zombie
The only known way to get to -1HP without dying is by starting a death process during some cutscenes. Dying locks Crash movement, but some cutscenes unlock it. It's believed that cutscenes that change Cortex' state (normal, Doc Amok or Pipe) and/or teleport Crash do that. There are three ways to get rid of Zombie.
 * Dying. It will respawn you at the last checkpoint you got before Zombie or world checkpoint you got during Zombie.
 * Grabbing a mask. It will make your health get back to normal, but still won't be able to grab checkpoints you triggered/locked until you die.
 * Entering cutscenes.

Hub 1 Zombie (100%)
In Totem Hokum you can get Zombie at the cutscene after Doc Amok. It is used to go faster through the watchmen section and skip different puzzles until the middle of Ice Climb.

Dingodile Skip (100%)
In Boiler Room Doom you can get Zombie at the farting cutscene. It is used to get gems faster and without hitting checkpoints, so you can die and respawn in another level instead of fighting Dingodile (Classroom Chaos).

Zombie Cortex
Cortex can get Zombie using the boat linking the first two hubs.