The only voice I know of that he does is Plankton. Well, that's good enough for me! I think he does the perfect voice for Plankton. I mean, I suck imitating Plankton, so in my opinion, he does an incredible job at it. Also he's good at the many other voices he does on SpongeBob, such as that insane guy who yelled "CHOCOLATE!!!" on Chocolate with Nuts, Larry the Lobster and the additional voices on SpongeBob SquarePants. He can do some pretty darn good screams as well. In addition to the voices he does, I also like the episodes he writes on SpongeBob, such as Plankton, Walking Small and Plankton's Sinister commentary on the SpongeBob vs. The Big One DVD. I really hope he does more voices in the future, but till then, I hope he continues doing Plankton.
Please read the following before uploading
Do not upload anything which you do not own or are fully licensed to upload. The images should not contain any sexually explicit content, race hatred material or other offensive symbols or images. Remember: Abuse of the TV.com image system may result in you being banned from uploading images or from the entire site – so, play nice and respect the rules!