The Way of the Sponge
S8:E27Sandy introduces Fuzzy Acorns, "the greatest karate master ever", to SpongeBob. The master is training Sandy to earn the "blacker belt", the highest belt in karate. SpongeBob wishes he had a belt, which Fuzzy overhears and tells SpongeBob that if he wants one, he has to earn it. Fuzzy offers to train SpongeBob so that he can earn the belt, which he reluctantly accepts.