Experiment 318 was the 318th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to chortle.
318 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 Chortle.
The first 624 experiments, including Chortle, were round up by Leroy and taken to a stadium to be destroyed. However, Lilo, Stitch, Jumba, Pleakley, Reuben and Gantu arrived before the experiments could be destroyed.
It is unknown whether or not Chortle participated in the following battle between the experiments and the Leroy clones.
The Leroys soon gained the upper hand in the battle, but were defeated when Lilo, Stitch, Reuben and several other experiments performed the song Aloha Oe, which caused the Leroy army to shut down due to the original Leroy's failsafe.
Chortle is a pink koala-like experiment with oval blue eyes, rabbit-like ears, a round nose, a wide mouth and a fox-like tail.
Chortle's powers somehow relate to chortling, and considering he is categorized under the series 3 experiments (Psychological), it can be assumed he makes people chortle. However it is also possible Jumba designed him to disrrupt important meetings by chortling at inaproppriate times.