Animaniacs (SNES)

Stage Select
A stage select exists in the game, but the method of accessing it differs between versions. In the Japanese version, hold Up+Y+Select and press Start during the opening cutscene.

For whatever reason, the button code was changed in the international versions, but the actual programming that checks it is skipped over completely. To enable the stage select in the US version, use Pro Action Replay code, start a new game, hold Up, then press Start during the opening cutscene.

Test Levels
Three test levels can be accessed by selecting the last three options (TEST 1 through TEST 3) on the stage select screen.

TEST 1 is a balloon jumping stage. It has several silver coins and 6 golden coins, and the default music is set to "Looney Tune". The exit leads to TEST 2.

TEST 2 is the same level, but without coins and with one guard chasing you. The default music is "Animaniacs main theme", but it doesn't loop.

TEST 3 is the same as TEST 2, but with a broken background palette. The default music is set to "Pinky and The Brain main theme", and if you stay in this stage for a long enough amount of time, the music will play backwards. Also, it seems impossible to defeat the guard, and you cannot access TEST 3 via TEST 2 because the exit is not defined. The only way to enter TEST 3 is using the Stage Select code.

The real purpose of these 3 rooms is unknown. They may have been used to test physics, AI and palette.