Experiment 566 was the 566th genetic experiment created by Jumba with Hämsterviel's funding. He was designed to drill potholes. 566 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. Against statistically unlikely (but not impossible) odds, several experiment pods landed in one location: Mrs. Hasagawa's yard, 566's pod being one of them.
At an unknown point, Mrs. Hasagawa mistook 566's pod for an apricot and placed it in a colander for later consumption along with numerous other pods.
After Lilo and Stitch redecorated Mrs. Hasagawa's front yard without her permission, she was less than thrilled with the results, but decided to thank them for their hard work with the "apricots." The pods were then revealed, but before Lilo and Stitch could stop her, she washed them with a watering can, thus activating the experiments.
After his activation, 566 began to carry out his primary function by drilling potholes in Mrs. Hasagawa's floor. Lilo and Stitch believed the experiments to be a danger to Mrs. Hasagawa and, along with Jumba and Pleakley, decided to capture them all. 566 was then captured by unknown means.
566 and the other experiments were about to be taken away, but were returned to Mrs. Hasagawa when Lilo and Stitch saw how much she cared for them. 566 was then named Derrick.
The first 624 experiments, including Derrick, 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 Derrick 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.
- Derrick is very similar to Splat in that they both do construction work.
- Derrick is one of only four known experiments that wears a hat, the other three being Squeak, Frenchfry, and Slick. However, it is unknown if Derrick can remove his hat or not, while it is presumed Squeak can take off his hat since he appears with a fresh hat in the TV film finale after an earlier incident with the Evil-liminator, and Frenchfry's "hat" appears to be a part of his head, while Slick is wearing a true hat that he can remove.
- Derrick was activated off-screen.
- Derrick is one of the few experiments to not appear in the group photo at the end of Leroy & Stitch.