Kirby's Dreamland is a game released for the Gameboy in 1992 developed by HAL Laboratory and published by Nintendo. The game had sold up to 5 million copies, making it one of the best-selling Gameboy games of all time. Kirby is still one of Nintendo's best-selling franchises.
At the end of the game after finishing the story, a password is given to the player to unlock a harder version of the game. The password is up, A, Select.
After finishing the game's extra mode, the player receives a password to the config mode, where the player can listen to the soundtrack and edit the game. The password is down, B, Select.
After waiting a short time while pausing the game, Kirby will do a secret dance.