Preston was built to be a friendly and helpful aid, but unfortunately, due to a malfunction, the end product was anything but. He is instead a pitiless thief and criminal, obsessed with wealth. He was willing to sink to the lowest depths to complete his agenda, willing to dispose of anyone or anything that interfered. He'd also be willing to brutally mince up sheep or humans to make more valuable dog meat.
A portrait of him with his inventor indicates that perhaps at one time, Preston was the faithful companion he was designed as before his more sinister programming came to be.
He feels no loyalty towards Wendolene, whom he had forced into his sheep rustling scheme and had take part in his slaughter of the innocent animals. When she tried to stop him from attacking Shaun, he locked her up with the rest of them and did not hesitate to add her to the herd that was to be minced next.
After being destroyed by Shaun and rebuilt, Preston became a harmless and good friendly dog again.
In "The Curse of the Ramsbottoms" comic strip from the book Wallace & Gromit and the Lost Slipper, he is now a cyber-butler in the employ of Wendolene and her evil fiancé, the cheese magnate Rhett Leicester with his army of gnomes.
A Close Shave
Preston goes rogue and plans to steal sheep for their wool, before deciding to turn them into his own brand of dog food. After discovering Wallace's Knit-O-Matic, he decides to steal the blueprints so he can make his own version for shearing and mincing sheep, the Mutton-O-Matic. When Gromit tries to reveal his plot, Preston frames him for his own thefts and killings.
With Gromit in prison, Preston has free reign over the clueless Wallace and the non-threatening Wendolene. Preston's plan is eventually foiled by Shaun, who frees Gromit. Preston is sucked into his own grinding machine while trying to use it on Wallace and Wendolene, and is crushed into pieces. He is eventually rebuilt by Wallace and seemingly restored to his original, kinder self.
- Preston is named after Preston, the county town of Lancashire, which Nick Park comes from.
- Preston might be a parody of the T-800 Terminator due to being covered in synthetic skin and is a robot. Also, both Preston's and the first T-800's fates were similar: Preston was crushed by a machine and the terminator was crushed by a hydraulic press.
- He resembles several different breeds of dog, but he mostly looks like an anthropomorphic presa canario.
- Preston also shares similarities with the robots from the Simpsons episode, Itchy and Scratchy Land, as well as the animatronics from the indie survival horror game Five Nights at Freddy's (though this can be considered merely coincidental as the game was released more than a decade after A Close Shave).
- Apart from growling and roaring, Preston is silent.
- Unlike Feathers McGraw, who only threatened to kill Gromit, Preston killed several sheep very inhumanely.
- Due to this fact, he is one of the darkest characters Aardman has created, alongside Mr. Arnold Hugh from Stage Fright, Mrs. Melisha Tweedy from Chicken Run, and Piella Bakewell from A Matter of Loaf and Death.
- In fact, Preston shares quite a few notable traits with Mrs. Tweedy:
- Both are paired up with fearful subordinates, one an equally intelligent but benign female wool farmer called Wendolene Ramsbottom, the other, an equally cruel but less intelligent male egg farmer called Mr. Willard Tweedy. Both Preston and Melisha are disappointed with the current business in which they work.
- In Preston's case, it’s wool-making, and in Mrs. Tweedy's case, it’s egg-counting. Both aspire to become rich by butchering up their livestock using vast machines to mass-produce food, and crafting their public image as sweet and friendly. In Preston's case, it’s mutton-flavored dog food, and for Mrs. Tweedy, it’s chicken pot pies.
- Melisha and Preston both had their former subordinate rise against them, but their species are different.
- Preston is a cybernetic canine and is very silent, and Melisha Tweedy is a human and is very capable of speaking English.
- According to the Wallace & Gromit: Cracking Contraptions Manual, Wallace was the one who rebuilt Preston as a friendlier, more "domesticated" robot dog near the end of A Close Shave.
- A mechanical hand identical to Preston's robotic hand can been seen in A Shaun the Sheep Movie: Farmageddon, having been thrown by Lula while she is searching for her teddy in the spaceship.