Cheat: PaRappa's Voice Change
PaRappa (and Chop Chop Master Onion) is getting a mild revival thanks to PlayStation All-Stars Battle Royale. If you still have the original PlayStation game or want to pick it up digitally in the PSN store, here's a unique code you may not have known about.
If you want to play other character voices from the game, complete the first two levels with a Cool rating. Then press X, X, X, Triangle, Circle, Triangle, Square, Square, Right, Left, Square, X and finish then the next level. On level 4, press X, Square, Triangle, Circle, and X. Now PaRappa's voice will change. Hold R1 and press Circle or Triangle to cycle through the other voices.