- Stitch (a.k.a Experiment 626), the main protogonist of the series. He is voiced by Benjamin Diskin.
- Yuna, Stitch's best friend.
- Angel (a.k.a Experiment 624), Stitch's love interest and girlfriend.
- Genie and Iago the Parrot, originally from Aladdin. Iago is voiced by Gilbert Gottfried. Genie is voiced by Ian James Corlett (season 1) and Dan Castellaneta (season 1 episode 10 and season 2).
- Agumon, a Digimon that is originally from Digimon Data Squad. He is voiced by Brian Beacock.
- Phantasmo, one of Stitch's many cousins, he, Richter, Clip and Sparky assist Stitch in bringing down Dr. Sputnikies. He is voiced by Nancy Cartwright.
- Richter, one of Stitch's cousins, it is thanks to him that the world is safe and assists Stitch along with Sparky, Clip and Phantasmo. He is voiced by Tress Macneille.
- Sparky, one of Stitch's closest of cousins, he helps Stitch along with Richter, Clip and Phantasmo. He is voiced by Frank Welker.
- Clip, one of the first female experiments to appear, she is one on Stitch's closest cousins and helps him along with Richter, Sparky and Phantasmo.
- Doctor Sputnikles, the main antagonist of the series who is the friend of Dr. Hamsterviel. He is voiced by Edwin Neal.
- Phil Hayes and Garry Chalk as Slash and Tanker: They are a pair of robots created by Sputnikles to capture 625 experiments. The two are extremely incompetent to the point where they struggle with even simple tasks, and are highly gullible, easily being tricked by Stitch no matter how bizarre, obvious, or pathetic his disguises are. Their constant failures result in the two regularly being abused, both verbally and physically, by Sputnikles. They also constantly fight about which of the two are Sputnikles' "favorite" but mostly just fight in general. This is one of the main reasons that they always fail at catching the blue alien. Slash was originally created by Sputnikles to be a super-robot that could easily catch Stitch for him, but a malfunction created Slash, a product almost the exact opposite of what Sputnikles wanted. He attempts to clone Slash sometime later, but Slash pulls a lever that Sputnikles did not, resulting in the creation of Tanker. Slash resembles a tall, humanoid kangaroo, and Tanker is a small green robot that resembles cross between a crocodile and a turtle with tank tracks and crab-like claws replacing his hands.
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