Tricky Terrarium

Tricky Terrarium is an anomalous level that can take the place of Big Boo's Haunt in certain copies. The course takes place inside an insect terrarium in the Courtyard, which Mario has to shrink down in order to enter. It's thought that this level was replaced by Big Boo's Haunt during development, as they share some assets and the same entrance location.

Layout
The entrance to the course is located on the grass in the Courtyard, in the same spot that a Boo would normally appear with the entrance to Big Boo's Haunt. Inside, the course is themed after an insect terrarium. The walls are made of translucent plastic, showing the tall blades of grass surrounding the cage. Leaves, sticks, and other items are located throughout the level to be used as platforms. A small area has water, containing Skeeters as the only aquatic enemy.

Enemies
The enemies found throughout the course are all insects or arachnids, sticking to the theme. Scuttlebugs and Skeeters can be found throughout the level, along with the unused enemy Hopper. It's thought that Hopper was designed for this course, but went unused early in development along with the course.

Theorizing
The theme of this level may have seemed redundant, as Tiny-Huge Island already had a similar design involving Mario facing tiny enemies at a bigger scale. It being replaced with Big Boo's Haunt may explain the strange cage used to enter said level.