Inside the files of Bloons Super Monkey 2, there are multiple files relating to unreleased worlds. As of now, there are only 3 unused worlds inside BSM2. It is unsure if these were ever implemented into any version of the game.
The first unreleased world had its name revealed by Tim Haywood in his Bloons Super Monkey 2 music album. The Track was called BSM2 - World 5 Sky Space. In the game files, the world background was found. it had lots of stars in background, a planet that looks like saturn, and what appears to be a black hole. Sky Space by Tim Haywood.
Big Wave BeachEdit
This is the unofficial name of this unreleased world is Big Wave Beach, as it consists of just a few islands, lots of water and is very similar to the Bloons Tower Defense 5 Map, Challenger Deep. No music released.
This is the only world to look like an actual planet, and it looks like earth. At the bottom we have a continent surrounded by water, then more continents and soon it looks like Sky Space in the sky with the moon this time and less stars.