Dr. Jumba Jookiba is the creator of 628 illegal genetic experiments, all of which eventually crashlanded on the islands of Hawaii on the planet Earth. Judging by several morphological similarities between himself and his various creations, it could be assumed that either they are mostly or all based upon species native to his homeplanet of Quelte Quan or that they possess a portion of his own DNA.
The experiments are physically formidable, often displaying superior strength and resilience compared to most other life forms; even though very few are larger than a Human child. They're capable of surviving in space vacuum and can also be dehydrated and stored as small pods, which will be restored to life immediately when in contact with water. Although all the experiments are sapient, their ability to speak is highly variable, with some being far more articulate than others.
Upon creation, each experiment is assigned a number and a primary function suited to their own particular biology and skill. Created to sow chaos across the galaxy, they can nevertheless by befriended, and eventually came to see themselves as a large family, referring to each others as "cousins".