Chompies

Chompies are a removed enemy from Super Mario 64. They take the form of a blue Chain Chomp that is considerably smaller than their black counterparts, thus making them more similar to the appearance that Chain Chomps had in Super Mario Bros. 3. They are usually reported in courses taking place in outside areas, such as Bob-omb Battlefield, Whomp's Fortress, and Tiny-Huge Island, though they have also been reported in places like Hazy Maze Cave, Big Boo's Haunt and several Bowser levels.

Behavior
Most reports describe the behavior of Chompies as a mix of multiple enemies found in standard versions of Super Mario 64. Like the regular Chain Chomp, they are usually described as either being attached to a post or staying in one specific area passive until approached. However, their typical behavior more resembles Piranha Plants; They will stay in one position, entirely still besides for their idle animation. When approached by the player, they will begin to wiggle around on the ground, before lunging at the player, much like the black Chain Chomp. Afterwards, they will pause for a few seconds, before attacking again if the player is still nearby.

The Chompie attack is unique, as several players have described it having the unique side effect of making the player launch upwards as if they had touched lava. Others say that Mario will also run around uncontrollably, even though no burn effects are present, though this is less common. Another unique aspect of the Chompie is that many have claimed it will refuse to attack the player if approached with the Metal Cap, instead whimpering and trying to jump away.

The most common method of defeating a Chompie is waiting for it to pause after an attack, then grab it's chain, swing it around, and throw it, much like the Bowser boss fights. Upon hitting any surface, they will explode, similarly to Bob-ombs. If the Chompie is attached to a post, the player will either need to ground pound it and then grab the chain, or ground pounding the post will cause the Chompie to flee, much like the regular Chain Chomp. Alternatively, most reports of Chompies say that they can instantly be defeated with the Metal Cap, which is likely why they try to flee. Defeating Chompies usually only rewards the player around 4 coins, though blue coins, single coins, and even red coins have been reported.

Missions
Some reports of Chompies mention encountering missions in the game related to Chompies. One example of a commonly documented mission is in Cavern of the Metal Cap, where instead of having to collect 8 red coins underwater using Metal Mario, the player is required to defeat 5 to 7 Chompies in order to acquire the Star. This mission is described as being rather trivial compared to the red coins mission, due to the Metal Cap commonly instantly defeating Chompies. There have also been reports of a mission related to Chompies named Guard Chomps on Duty overriding the regular Chain Chomp's star, Behind Chain Chomp's Gate, where instead of a cage and a Chain Chomp appearing in Bob-omb Battlefield a strange wooden platform surrounded by fences with 3 Chompies inside of it takes its place, and instead of having to ground pound the Chain Chomp's pole and destroy the gate, the player has to defeat all 3 Chompies to spawn a star, similarly to Lethal Lava Land's Bully the Bullies mission.

Theorizing
It is commonly believed that Chompies were removed from the game due to their similarities to several other enemies, and the existence of the black Chain Chomp making it so the game has two enemies of the same species, which otherwise only occurs with the Piranha Plant and Piranha Flower as well as some of the bosses, in order to ensure enemy variety. Alternatively, the Chompie may have been made before the black Chain Chomp, only for the developers to decide to use the one seen in Bob-omb Battlefield instead for one reason or another, perhaps due to the complexity of the enemy's behavior compared to most others seen in the game, or being deemed too difficult for players in the places it would've been located in.