Jackie Chun is a parody reference to martial artist and actor Jackie Chan, which appears in the Dragon Ball manga and anime works. It was the assumed name that Master Roshi used when fighting in the World Martial Arts Tournament.
Master Roshi entered the World Martial Arts Tournament as "Jackie Chun" to anonymously teach his students a valuable lesson: that there would always be someone stronger than them somewhere in the world. He fights and defeats Krillin, but causes suspicion about his identity when he has to use his signature Kamehameha attack at the outset of the fight to keep himself in the ring. The fight ends with the characters still unsure of his identity.