In 1992, seven years before the premier of SpongeBob SquarePants, the late Stephen Hillenburg was enrolled in CalArts' Experimental Animation Program. As a student, he created his first cartoons, including "The Green Beret" (1992) seen above, which landed him his job at Nickelodeon, working on Rocko's Modern Life and, later, developing SpongeBob SquarePants.
Watch Stephen Hillenburg's fantastic pre-SpongeBob student animation from 1992