Smiler, A.K.A. Experiment 309, is an illegal genetic experiment created by Jumba Jookiba. He is designed to incapacitate targets. His one true place is as a dentist assistant.
Experiment 309 was the 309th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to incapacitate targets (does so by emitting a nitrous oxide that causes an individual to become relaxed, slap happy, and incapacitated).
309 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 Smiler.