Although he is sweet and loyal, Jock can be the most aggressive dog in Lady's circle of friends, in spite of being the smallest. Nevertheless, he values his loved ones and makes an effort to make such a fact clear, on a consistent basis. He treats Lady as his own relative, watching her grow alongside Trusty and continuously congratulates the spaniel on her many accomplishments, such as the day she received her first collar. He also takes it upon himself to mentor the young pooch, teaching her the ways of welcoming a new baby into the household and telling her stories of Trusty's past and such.
He is notably the best friend of his neighbor, Trusty who, like Lady, he treats like a relative, along with the lines of a brother. The two get along fine, but with Trusty's bumbling ways and Jock's occasional aggression, they sometimes clash, though they never let it tamper their friendship for long, if at all.
Though he is essentially warm-hearted, Jock tends to be stingy at times, and never lets anyone see his prized collection of hoarded bones, even Lady, and he frequently praises things based on their expense, such as Lady's collar and the coming baby. This trait is a reference to the stereotype of Scots being frugal.
As seen in the film, some of Jock's dislikes include the exposure of his prized bones, Trusty's clumsiness and formerly "mongrels" like the Tramp.
In spite of his size, Jock is a fearless protector and will go to great lengths to protect the ones he cares about. This is shown when he threatens to attack Tramp (a dog twice his size) if he continues to "harass" Lady, and lastly when he risks his life to stop the dogcatcher's wagon from taking Tramp to the pound, as a way of apologizing to Tramp for mistreating him early on in the film, which shows he's honorable and admits to making mistakes.
Physical appearance
Jock is a short and slender gray Scottish terrier with black eyes, thick gray eyebrows, a gray mustache-like beard and wears a red collar with a gold diamond-shaped license, and later a plaid sweater.
Jock first appears while singing his song as he buries his bone in his secret spot, along with many other bones. Jock is then encountered by Lady who presents her brand new collar complete with a license. They then go to visit Trusty, who is dreaming. Jock confesses to Lady that Trusty has lost his sense of smell. The next day, Jock and Trusty visits Lady, as it is a perfect day until Lady tells them bad news. She tells the duo that Darling has not been treating her the same, along with Jim Dear.
Jock and Trusty quickly realize what's going on and as Jock puts it, "Darling is expecting a wee bairn." They start to describe what a baby is until Tramp arrives. Tramp shoves Jock out of the way to speak to Lady, which upsets Jock, who barks at him to keep away from Lady.
Jock later reappears near the end of the film after Lady and Tramp got to know each other. At this point, Lady cannot stand him. And when Tramp returns after being separated by the dogcatcher, Jock is prepared to attack when ready, although Lady claims it's not necessary. However, upon hearing that Tramp saved Jim Jr. from the attacking rat and killing it, Jock and Trusty realize that Tramp is really not all that bad for a dog. Jock felt very ashamed for misjudging Tramp badly, fearing that Tramp will be put down by the pound workers.
To redeem themselves, Trusty and Jock rush to the dogcatcher's wagon and attempt to stop it and save Tramp. They succeed in saving Tramp, but unfortunately, Trusty is run over when the wagon crashes. Jock nudges his best friend, but Trusty does not move, leading Jock to howl in mourning. At Christmas, Jock joins Lady and Tramp, who have mated with four puppies. Trusty survived the crash with only a broken leg and joins the celebration as well. As the feisty Scamp unravels part of his plaid sweater, Jock congratulates Lady and Tramp on their puppies, also noting Tramp's collar like he did with Lady from the beginning.
Jock makes another cameo in the spin-off TV series in the pilot episode, "Home is Where the Bark Is". When Lucky asks Jock for a ride in his human's boat, after they miss the ferry, he at first turns them down before realizing that they are the puppies that Pongo and Perdita sent out a barking chain message about. He is then all too happy to use the boat to help the pups cross the water (his human is asleep during this sequence).
Later, as the pups race Cruella back to the Dearly Farm, Rolly frets that there is no way they can outrun Cruella's car. Jock then tells the pups to get going as he sends out another barking message to the farm animals so they can set up traps to delay Cruella. In the series, he is shown to wear a red sweater, which he is seen wearing at the end of the original film.
Jock reappears in the sequel. He and Trusty remain close to Lady and Tramp, being known as "Uncle Jock" to their puppies, Annette, Collette, and Danielle. and Scamp He and Trusty are first seen as they watch happily while Lady, Tramp, and their family pass through during a stroll. They later appear after Scamp ran off and the news is brought to their attention by Annette, Collette, and Danielle. Jock joins Lady, Trusty, and Tramp as they search for Scamp. Trusty and Jock continue to search and are eventually reunited with Scamp and join the family as they welcome Angel to the family.
Jock makes a handful of cameos in House of Mouse. Jock's most notable appearance is in "Pluto Saves the Day", where he joins an all-dog band singing "Everybody Wants to Be a Woof". Later in that same episode, he is seen with the other Pet Shop Dogs fighting off Pete (who's disguised as Snow White) and then chasing him out along with the rest of the dogs and Pluto.
In Once Upon a Studio, Jock appears with Trusty outside the studio, with Trusty once again talking about his grandfather, Old Reliable. He later appeared in the group photo along with the rest of Disney characters.
