Preston was a robotic dog created by a scientist to help with his wool factory. After the scientist died, Preston took care of his daughter, Wendolene, who now owns the wool factory and shop.
However, Preston went rogue and made a scheme to steal sheep and turn them into his own brand of dog food. He had a huge, diabolical machine that would grind the live sheep to meat and dispense them into cans. The newspaper mentions that some of the sheep were killed on the spot instead of stolen, most likely due to Preston's violent temper. When Gromit tried to unveil his plot, Preston framed the other dog for his own thefts and killings.
With Gromit in jail, Preston had free range over the clueless Wallace and the nonthreatening Wendolene. Preston's plan was eventually foiled by Shaun, who broke Gromit out of jail. Preston was sucked into his own grinding machine while trying to use it on Wallace and Wendolene, and was crushed into pieces. He was eventually reassembled, and seemingly restored to his original, kinder nature.
- Preston is most likely a parody of The Terminator. Both their fates are similar, Preston is crushed by a machine and Terminator by a press.
- Preston is considered to be one of most evil Aardman villains as well as Trumper, Mrs. Tweedy and Piella Bakewell although he is the only one of these four to redeem themselves.
- His true robotic form resembles Mechagodzilla. Like the original Mechagodzilla too, he also wore a fake skin disguise to conceal his true identity.
- He is also similar to Long Eared Jack as both were thought to be real animals but only to be discovered as robots near the end of their films. However whilst Jack was being controlled by Carols, Preston had a mind of his own.
- In the film, when Preston turns on Wendolene, she tells him "Daddy didn't create you for this!" Overshadowing his eventual reveal as a robot.
- Preston is seen happily smiling on the painting of him and Wendolene's father, implying that the death of his creator made him bitter and selfish.