of the educational directors asked him if he would be interested in creating an educational comic book about the animal life of tidal pools. He created a comic called The Intertidal Zone, which he used to teach his students. It featured anthropomorphic forms of sea life, many of which would evolve into SpongeBob SquarePants characters—including "Bob the Sponge", the comic's co-host, who resembled an actual sea sponge, as opposed to his later SpongeBob SquarePants character, who resembles a kitchen sponge. He tried to get the comic published, but the publishers he approached turned him down. During this time, Hillenburg also started attending animation festivals such as the International Tournée of Animation and Spike and Mike's Festival of Animation, where student films from the California Institute of the Arts (colloquially called CalArts) were shown. He determined that he wanted to pursue a career in that field. He had planned to take a master's degree in art, but instead of "going back to school for painting", he left his job in 1987 to become an animator. Hillenburg enrolled in CalArts' Experimental Animation Program in 1989. About this decision, he said: "Changing careers like that is scary, but the irony is that animation is a pretty healthy career right now and science education is more of a struggle." He studied under Jules Engel, the founding director of the program, whom he considered his "Art Dad" and mentor. Impressed by The Intertidal Zone, Engel accepted him into the program. Hillenburg said, "[Engel] also was a painter, so I think he saw my paintings and could easily say, 'Oh, this guy could fit in to this program.' I don't have any [prior experience in] animation really." Hillenburg graduated in 1992, earning a Master of Fine Arts in experimental animation. During his time at CalArts, he briefly drew comics for the surfing magazine KEMA in 1990. Animation career Early works Hillenburg made his first animated works, short films The Green Beret (1991) and Wormholes (1992), while at CalArts. The Green Beret was about a physically challenged Girl Scout with enormous fists who toppled houses and destroyed neighborhoods while trying to sell Girl Scout cookies. Wormholes was his seven-minute thesis film, about the theory of relativity. He described the latter as "a poetic animated film based on relativistic phenomena" in his grant proposal in 1991 to the Princess Grace Foundation, which assists emerging artists in American theater,