Jet Grind Radio Unlockables and Easter Eggs (GBA)

Jet Set Radio (Jet Grind Radio in the United States), is a video game released by Smilebit on 1 November 2000. Jet Set Radio was designed for the Sega Dreamcast, although a version of the game was later released for Game Boy Advance. A sequel called Jet Set Radio Future was released for Xbox. Jet Set Radio was announced at the Tokyo Game Show in 1999 and generated a prodigious amount of press attention due to its use of the now-common 3D rendering technique, cel-shading, which was considered cutting edge at the time. Cel-shading allows for a "cartoon-like" appearance of rendered objects. Jet Set Radio was released in Japan on 29 June 2000.

The US release, re-titled Jet Grind Radio, contained two new maps, various new songs, and other in-game content designed to increase the game's appeal to Western audiences. This version also allowed the user to connect to the Internet via SegaNet and download user-created graffiti tags, or upload tags of their own. Sales of the game were relatively low, but despite the commercial failure of Jet Grind Radio, it has gone on to achieve a cult following in the gaming community. (Wikipedia)

Unlockables

Unlock Poison Jam
Beat all Kogane-Cho levels with a Jet ranking

Unlock Professor K as playable character
Play through the game (beat ''Final Stage'') and save the game. From now on Professor K from Jet Set Radio can be chosen as a playable character. He is located between Garam and Beat on the character selection screen (you can't see him dancing like the other characters, only his picture appears).

Unlock the Love Shockers
Get a Jet ranking on all Shibuya-Cho levels.

Unlock the Noise Tanks
Get a Jet ranking on all Benten-Cho levels.

Easter Eggs

Change the Sega intro
If you start the GBA with Jet Grind Radio and continuously press the A button until the Sega logo appears you will hear a person scream the word Sega instead of the normal longer chorus.

Probably the coolest GBA title I've seen lately: