Upon encountering each experiment, Stitch's human friend and partner Lilo gives the experiment a name just as she gave Stitch his name. The two then attempt to rehabilitate the experiments and find a purpose for them on Earth that suits their specific abilities, referred to as the "one true place" they belong.
Stitch, inspired by Hawaiian terminology, sometimes refer to some experiments as his "cousins" and considers them all a part of his ʻohana, or "extended family". All of Jumba's original 626 experiments have their names and numbers listed alongside the credits in Leroy & Stitch.
The first digit of the experiment numbers reflect what series of experiment they belong to. The unofficial series of experiments, as stated by Jess Winfield, one of the executive producers, are as follows:
- 0-Series: Jumba's test batch, including many household helpers.
- 1-Series: Civic disturbances.
- 2-Series: Technological and scientific.
- 3-Series: Psychological.
- 4-Series: Mysterious series of mostly failed experiments (later Military).
- 5-Series: Elemental manipulators.
- 6-Series: Battlefield or doomsday experiments with galactic implications.