Retro, A.K.A. Experiment 210, is an illegal genetic experiment created by Jumba Jookiba and a character in the Lilo & Stitch franchise. He is designed to reduce people, animals, enemy weapons, and technology to a more primitive state; wrapping his tongue around the object or victim and spanking his bottom three times will reverse the de-evolution. His one true place is at a wildlife park, resurrecting extinct animals for a Mesozoic zoo.
Note: this is only a parody and most likely will never happen in real series
Outside of Lilo and Stitch series, his current 'ohana and partner is Sandy Cheeks (from Spongebob Squarepants). Sandy discovered Retro while she takes a round trip back home to Texas, in a museum, causing massive damages after he revived a fosilized Tyronosaurus Rex, which made Sandy jumped into action to stop it. After she stopped the disaster before it get could worse, the Texas museum management captured Retro as he was responsible for massive damage and sentenced to be arrested by the authority. However, she pleaded them to not confine the genetic experiment in prison cell, but rather take it as her own pet, which the management having doubts at first, but later agreed.
After the incident, she already knew that Retro had an unusual power to turn extinct and prehistoric beings to turn back to life, and somehow she was interested of taking it home back to Bikini Bottom for further analysis. Just after her stay in Texas, she meet up with Jumba Jookiba, the original creator of Retro, telling him that it wasn't an ordinary magical creature like she'd thought, but rather an illegal genetic experiment who can turn everything back to prehistoric times. He also told Sandy on how to reverted it back to present look somehow (by beating his back 3 times while licking a prehistoric item/being). She made her mind up to still take Retro, but this time as her experiment and research assistant than a pet, which Jumba never asked her that question yet, but still glad to hear it from her.
He is currently assisting Sandy for her prehistoric research, and also, turning any thing that Sandy owned back to prehistoric value. He is also acted as a guardian of Sandy's house and all of her properties she owned. He is also befriended by Spongebob, and Patrick, but sometimes turning them into a jurassic prehistoric beings just to stop them from messing Sandy's belongings.