Highlight Arcade mode and press Start. Then, highlight any of the difficult settings and press Right, Right, Right, Right, Right, Right.
Another mode
At the game mode selection screen, press Down, Down.
Change on-screen characters
Hold Left or Right, then press Start.
Change playing style
Hold X then press Start.
Hidden mode
At the song selection screen, press Select, Up, Down, Up, Down, Up, Down, Up, Down.
Left mode
At the song selection screen, press Select, Left, Left, Left, Left, Left, Left, Left, Left.
Little mode
At the song selection screen, press Select, Left, Down, Right, Down, Left, Down, Right, Down, Up.
Maniac mode
Unlock Another mode, then press Down, Down at the game mode selection screen.
Mirror mode
At the song selection screen, press Select, Left, Right, Left, Right, Left, Right, Left.
Return to normal mode
Unlock Another mode or Maniac mode. Then, press Up, Up at the game mode selection screen.
Right mode
At the song selection screen, press Select, Right, Right, Right, Right, Right, Right, Right, Right.
Shuffle mode
At the song selection screen, press Select, Up, Down, Left, Right, Down, Up, Right, Left.
Super mode
Press Up, Up, Down, Down, Left, Right, Left, Right at the title screen.
Unlock Everything and Bypass Lockout Protection
Upon booting the game, keep mashing Select + Start rapidly until a confirmation tone is heard. When done, the Mode Selection screen should appear instead of a Health & Safety screen. All 5 unlockable tracks, as well as information, Nonstop, Paint, Event and Endless modes become available.