Substein, A.K.A. Experiment 387, is an illegal genetic experiment created by Jumba Jookiba. He is designed to bore people by telling facts about buses.
Experiment 387 was the 387th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to bore people by telling facts about buses.
387 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 Substein.