Chum, A.K.A. Experiment 315, is an illegal genetic experiment created by Jumba Jookiba. He is designed to betray trust (does so by acting really friendly at first, and when you feel secure in your friendship, he betrays you and hurts your feelings).
Experiment 315 was the 315th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to betray trust.
315 and the other first 624 experiments were deactivated and smuggled to Earth by Jumba during his mission to capture Experiment 626.
All of the experiment pods were released and scattered across the island of Kauai.
At the unknown point, he was activated, captured, tamed and named Chum.
Reprogrammed not to betray the people he befriends.