There's a set of rather useful features that are, for some reason, disabled by default. However, they can be unlocked via a simple "code" on the title screen by clicking on the "N" in "MARIO PAINT" to start the staff roll and, when "PROGRAMMER NORIAKI TERAMOTO" appears, holding the right button and clicking the "N" again. By doing so, the player will unlock a series of available commands, most of which are utilized through the right button.

The list of (currently known) hidden features are as follows:
• Right-clicking anywhere on the screen will activate Undodog (with a few exceptions).
• Right-clicking on the canvas in the Stamp Editor will sample the pixel color underneath the cursor.
• Four new rotation options are available in addition to the old horizontal/vertical flip options (see screenshot).
• Pressing L + R + Start + Select on Controller 2 will reset the game (code will need to be entered again).