Poo is played by Steve "D-Lux" King, who I believe hosts the radio show Very Good Music (and I'm really guessing the show he hosts off the top of my head, if I'm wrong, please please please correct me). If you've heard the show before, you know the voice.
I know I'm gonna have to listen to that, but that's not where I've heard it before. He must just sound alot like someone I've heard before - possibly on a Wyclef Jean CD.