Ganbare Goemon (known as Legend of the Mystical Ninja in North America and Europe), is a prolific video game series produced by Konami.

These games revolve around the main character Goemon and his exploits. As the name suggests, his character was loosely based on Ishikawa Goemon, the noble thief from Japanese folklore. While the early games of this title emphasized Goemon as a noble thief, he eventually became more of a standard video game hero character. Trademark elements of his appearance would be his blue bushy hair and his weapon of choice, the Kiseru.

The universe of these games is of a cartoony, mystical Feudal Japan, where every bit found in the folklore and legends about Japan are true. Although the series has its roots in action adventure, the Ganbare Goemon series features games from a diverse set of genres including RPG, puzzle game, and board game. Ganbare Goemon has proven to be widely popular in Japan, because along with its long video game series (which continues to this day), a wide series of merchandise, and several anime and manga series have been created, based on it.
(Wikipedia)

Please note: These codes work for Ganbare Goemon: Toukai Douchuu Ooedo Tengurigaeshi no Maki

UNLOCKABLES

Alternate costumes
Collect all 30 Elephant Statues to unlock new costumes for all four characters.

Mystical Ninja History Lessons
Also, have the Game Boy Advance game Kessakusen! Ganbare Goemon 1+2 inserted. At select locations throughout the game, various characters from the Game Boy Advance game will appear and tell you things about Goemon's past.

Space-Manbo mini-game
Have the Game Boy Advance game Kessakusen! Ganbare Goemon 1+2 inserted. At the mini game menu, Space-Manbo will now be unlocked.

GAMEPLAY HINTS

Goemon New Age Shutsudou! reference
In the second town's underground prison, New Aged Goemon can be found occupying the second jail cell for his "crimes against the Goemon franchise".


Here is the opening video for Legend of the Mystical Ninja: