Glowing Rabbit

Glowing Rabbits are a type of Rabbit that can appear after 15 stars are collected in Super Mario 64 DS. They are white rabbits with a sparkle effect on them that can replace other Rabbits. 8 Glowing Rabbits must be collected to unlock the 5th door in the character select room and obtain a star.

Waluigi Connections
One of the many variants of the Waluigi theory known as ˥ Is Real 2401 states that the door unlocked by the Glowing Rabbits would have been used for Waluigi, but Waluigi was scrapped due to time constraints and was replaced with the Glowing Rabbits.

There is also another theory tied to the unused Big Star Key object that there is a hidden ninth Glowing Rabbit that would drop the Big Star Key that would change the door to unlock Waluigi. Some say that the ninth Glowing Rabbit is larger than the rest and is the Rabbit King mentioned in the Purple Prizes magazine.