Companions

Companions are an anomalous type of NPC found in some personalized copies of Super Mario 64, often compared to the partners seen in earlier Paper Mario games. They are described as special characters that can be unlocked and follow you around, being used to traverse areas and fight enemies. There is a diverse set of reported companions, all with varying mechanics and methods of unlocking.

Shared Aspects
Despite all Companions appearing to be unique, they all appear to follow a few set rules. They all have to be unlocked through fulfilling some form of requirements, they all appear to have applications when exploring levels, usually paired with heavy Dynamic Level Rearrangement, and a special attack used against bosses and enemies. Several Companions are reused characters seen in other places in the copy, though this is not always the case.

A majority of Companions are permanently unlocked and follow the player around forever, and can be swapped out for other Companions, but there are numerous reports of Companions that follow the player for a limited amount of time, usually tied to a specific mission in a certain level or larger scale side quest only found in personalized copies. If Companions are mission-specific, they commonly will not follow the player out of the level if they do not complete the mission.

Companions usually operate completely on their own, though several reporters have claimed that certain button combinations would allow the player to command their Companions, or they could be entirely controlled by somehow switching between the player and Companion, occasionally even using Multiplayer Mode to control the Companion.

The method of swapping between Companions is inconsistent, though generally appears as a special room, occasionally being found in an anomalous manifestation of the Rec Room, that would either automatically cycle between Companions or have a unique menu screen where the player can select a Companion.

List of Documented Companions
Take all of these documented Companions with a grain of salt, as a majority of them are unconfirmed and could be inconsistent between copies if real anomalies.

Bob-omb Buddy
The Bob-omb Buddy companion is one of the few Companions that has been reported as both a permanent Companion and a temporary Companion. They consistently appear in Bob-omb Battlefield. If they appear temporarily, they usually only join the player to aid in defeating Big Bob-omb and leave at the end of the mission. Notably, this Companion has also been reported to appear as a regular Bob-omb.

The Bob-omb Buddy's abilities are most commonly exploding to damage an enemy, and blowing up destroyable objects such as some boxes, or unique rock objects that cannot be destroyed without the Bob-omb Buddy. Notably, these abilities and the fact that Bob-omb Buddies are pink appear to imply a connection to Bombette from Paper Mario for the Nintendo 64, as they are very similar.

Yoshi
Yoshi has reportedly appeared as a Companion in some personalized copies, though has been considered a separate anomaly by some due to their difference from other Companions and their tendency to appear without other Companions in the personalized copy. Yoshi has reportedly been unlocked through talking to him on the castle roof, which usually only gives the player a special triple jump and 100 lives in the standard copy, or clearing a special level. Yoshi can supposedly appear as a temporary Companion for a specific level that requires Yoshi.

Yoshi consistently has the abilities of being a rideable mount for the player, and the ability to use their tongues to eat enemies and objects, even enemies that are usually invincible unless they are bosses or a large enemy. Notably, Yoshi can supposedly gain abilities such as fire breath if they eat certain objects such as the unused red Koopa shell object when spawned in through anomalous means. These abilities appear to isolate Yoshi from the other Companions, leading some to claim that Yoshi is a separate anomaly and should not be grouped with the anomalous Companions.

Tuxie
Tuxie, the baby penguin seen in Cool, Cool Mountain for the mission Lil' Penguin Lost, can reportedly function as a temporary Companion, only being accessible during their mission and leaves the player upon finishing the mission. They can attack by sliding into an enemy, appearing near identical to the slide that they do whenever they witness the player sliding, and can break any ice that could appear through Dynamic Level Rearrangement.

Lakitu Bro
One of the Lakitu Bros., the Lakitus recording the player throughout super Mario 64, has been reported to be unlockable as a Companion in some personalized copies of Super Mario 64. They commonly use the same abilities as regular Lakitus, with the ability to fly around and throw Spinies at enemies. They can reportedly be temporary Companions for a tutorial level such as the Other Castle Grounds, or can permanently join the player upon the beginning of the game.

Theorizing
It is believed that several characters reported as Companions were later reused as regular characters when Companions were scrapped due to a majority of Companions being characters existed in the main game. These characters have also been theorized to inspire several different partners seen in the Paper Mario series, potentially even inspiring the entire mechanic, with characters such as the Bob-omb Buddy and Lakitu Bro being compared to Bombette and Lakilester respectively.

It is not entirely known why Companions were scrapped, potentially being due to cartridge limitations or the developers finding it hard to implement the mechanic for a number of other reasons such as hardware limitations or not having enough characters to be Companions to make the mechanic worthwhile enough to be used by players, though during reimplementation by the Personalization A.I., more Companions could be generated that were not originally intended to be Companions, potentially explaining why a majority of Companions are reused characters found in the base game of Super Mario 64, and also why there are several Companions exclusive to specific reports.