Two of Nickelodeon's most memorable greenish-blue characters, Rocko's Modern Life's Filburt Shellbach and SpongeBob SquarePants' Plankton, are both voiced by Doug Lawrence (aka Mr. Lawrence), who was also a writer for both shows.
Bender Bending Rodriguez and blitzballer Wakka are both voiced by the same gloriously-mustachioed man, John DiMaggio, who's prolific career also includes:
You might best recognize Carlos Alazraqui as Reno 911!'s Officer Garcia, but he's also somehow the voices for both Rocko (of Rocko's Modern Life) and the talking Taco Bell chihuahua (of 90's commercials). On top of that, he's also: