Experiment 204 was the 204th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to eat socks, and thus make them disappear. 204 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.
204's pod was one of the twelve experiment pods recovered by Lilo and Stitch in "Drowsy". His was one of the final four experiment pods (among 102, 274 and 360) that Pleakley, with some assistance from Stitch, cataloged after being convinced to do so by Jumba.
At an unknown point after this, Experiment 204, named Nosox, was presumably activated and captured by Gantu, as he was mentioned in "Amnesio" when Hämsterviel said, "After you sent me a sock hider..."
Nosox appeared in "Snafu", and was freed along with Gantu's other captive experiments by Lilo, Stitch, and several other experiments in a rescue mission.
The first 624 experiments, including Nosox, 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 Nosox 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.
- Nosox is one of the rare experiments to have sclerae and pupils instead of solid black eyes, the others being Mr. Stenchy, Mrs. Sickly, Skip, and Clink.
- His name means "No Socks" (No Sox) because he is a sock hider.
- Nosox's pod color is green.
- Nosox is described by the experiment computer screen as, "Experiment 204. Primary function: Makes socks disappear."
- Nosox is one of the few experiments to not appear in the group photo at the end of Leroy & Stitch.