The unused Stadium level.
How to find the secret "stadium" test level in Scribblenauts Unlimited
How to access the Stadium using Cheat Engine.
The Stadium is an unused level in Scribblenauts Unlimited which exists in an unfinished state. It was used as a test level by the developers. This level can only be seen without hacking by using the "--autoloader" command line parameter in the PC version, and even then it only appears for a brief period of time and cannot be interacted with in any way. It is, however, possible to access this level through memory hacking.
The level is populated by several NPCs, many of which have simple shard missions to complete. There is a single Starite mission, "Yo! Two Hot Dogs!", which involves creating specific categories of food requested by fans. Said fans, however, are glitched; they are in mid-air toward the top of the screen, and cannot be seen except for their emotion bubbles. Upon completing this mission, or any of the shard missions in this level, a "Level Complete" screen will appear, even if more missions remain in the level.
"Stadium" would likely not have been the final name for the level, as it is too simple and doesn't fit with the theme of the other level names. The level doesn't have a final name that shows up in the game (it crashes when it attempts to display the name, so the current level must be changed in memory before this happens) but it is referred to as "S_STADIUM" internally.