Stage Select - On the title screen, press Left, B, Right, Up, Down, Left, Right, B, then A to access the Stage Select

Max Power (Famicom) - During gameplay, pause the game and press B, A, A, Up, Down, Down, B & Right. If done right, a sound will be heard.

Sound Test - On the title screen while 'push start' is flashing, press the following combination for a sound test. (Then select the tunes with A or B, play them with 'Start'.): Up, Left, Right, Down, A, B, A, Up

Double Speed & Rapid Rainbow - Anwhere during a stage (preferably at the beginning of the game), pause the game, input the following combination and unpause again (A jingle will confirm success): Up, Down, Left, Right, A, A, B, B