Princess Playroom

Princess Playroom, sometimes formatted Princess' Playroom or The Princess' Playroom, is an anomalous course found in personalized copies of Super Mario 64 DS. It is a level themed around pastel and crayon drawings, creating an art style similar to Yoshi's Island on the SNES. Unique enemies and Stars can be found in this level, and it is implied to be created from drawings made by a younger Princess Peach brought to life with the magic affecting the paintings.

Unlocking
The course can be accessed from the Rec Room through the 8-Star door that typically leads to the balcony room with the painting for Goomboss Battle. When this anomaly occurs, the door instead leads into a smaller version of the Rec Room with more props. The plushies of Power Stars and Koopa Shells found in the Rec Room are more common and scattered about, giving the room a messy and cluttered feel. On the wall is a framed picture of Princess Peach as a child, notably predating Baby Peach's appearance in Mario & Luigi: Partners in Time by a year. In the corner of the room is an easel with a canvas, showing a crayon illustration of a Toad and Goomba in a sunny field. This canvas is the entrance to the course and can be accessed by interacting with the picture rather than jumping into it.

Geography
Princess Playroom is an open level full of platforms that takes place above a blue sky drawn with crayon. The enemies found throughout the levels include Goombas and Amps that all feature a unique appearance, being textured with rough and scribbled shading to resemble paper drawings. Notably, the Goombas share a strong resemblance to an unused test enemy found in Super Mario Sunshine, referred to internally as Kug. Whether Kug was originally designed for this course or repurposed is unclear. The level consists of small fields of grass spread out across an open sky, similar to Rainbow Ride. Many giant, upside-down crayons serve as platforms between areas. The central point of the level is a smaller rendition of Princess Peach's Castle, which cannot be entered and is lacking in detail from the real counterpart.

Theorizing
Why this level was cut is unclear, although many theories exist. The unique art style of the course clashes with the others within the game and can cause low framerates and stuttering on some DS models. It is unknown how Mario would be unlocked in this course, if at all, as Goomboss Battle is replaced by this course and the Key cannot be found inside.