Splat is a large green experiment, with two cone-shaped yellow-striped antennae, yellow patches around his eyes, three yellow stripes on his rear legs and a small roller between his front legs.
Splat can use the small roller between his front legs to level roads and other surfaces.
Experiment 519 was the 519th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to level entire cities, with his deceptively small roller. 519 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 some point, 519 was presumably activated, captured, and named Splat.
Later, the first 624 experiments, including Splat, were rounded 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 Splat 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 ʻOe", which caused the Leroy army to shut down due to the original Leroy's fail-safe.