DJ Professor K
The loud-mouthed, fast-talking DJ for the titular pirate radio station from the Jet Set Radio series. In the games, he serves as a "narrator" of sorts, providing the player with exposition about the plot and characters. He has no direct involvement with the plot in Jet Set Radio, but in Jet Set Radio Future he frequently communicates with the player via walkie-talkie and at one point gets kidnapped (with his recording booth) by the villains. In the GameBoy Advance version of Jet Set Radio, he can be unlocked as a playable character after completing the final mission.
He also makes cameo appearances in SEGA Superstars Tennis, Sonic & SEGA All-Stars Racing, and Sonic & All-Stars Racing Transformed.