Old Man McGregor
- Portrayed by: Sam Neill
- Ax-Crazy: He tried to kill Peter and the Bunnies and nearly baked Peter into a pie. If he hadn't died of a heart attack, the movie never would've occurred and more importantly Peter would've perished.
- Big Bad: He is set up as one due to his unexpected appearance and anything revolving around him as well as him murdering Peter Rabbit’s father in cold blood.
- Demoted to Extra: Old Man McGregor's role in the film is pretty small compared to his part in the book, where he served as the Big Bad.
- Jerkass: He's a crotchety old grouch who has no remorse about the fact that he killed Peter's father and had him made into a pie, and gleefully tried to do the same to Peter himself. Old Man McGregor is such an asshole that Bea, despite trying to do so out of respect for his grandnephew, is unable to find anything nice to say about him after his death.
- Sacrificial Lamb: His death causes the movie's entire plot to happen.
- We Hardly Knew Ye: He dies of a heart attack at the first few minutes of the film, which culminates in the entire movie's plot happening.
