- “The name's Jock! [...] Heather Lad O'Glencairn, to you!”
- ―Jock to Tramp
Though 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 fried of his neighbor, Trusty who, like Lady, he treats like a relative, along the lines of a brother. The two get along fine, but with Trusty's bumbling ways and Jock's occasional aggression, the two sometimes clash, though they never let it tamper their friendship for long, if at all.
As seen in the film, some of Jock's dislikes includes the exposure of his prized bones, Trusty's clumsiness, and "mongrels", like the Tramp.
In spite of his size, Jock is a fearless protect, and will go to great lengths to protect the ones he care about. Three instances of this can be seen, where 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 dog catcher's wagon from taking Tramp to the pound, as a way of repaying the mutt for mistreating him early on in the film; showing he's an honorable dog that isn't afraid to admit mistakes.
Jock first appears while singing "Jock's Song" as he buries his bone in his secret spot. Jock is then encountered by Lady who presents her brand new collar complete with a license. They then go to visit a dreaming Trusty. As Trusty dreams, Jock confesses to Lady that unfortunately Trusty has lost his sense of smell. The next day Jock along with 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 realizes 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. Jock 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 can't stand him, and when Tramp returns after being separated by the dogcatcher, Jock is prepared to attack when ready although Lady claims it's alright. After Tramp redeems himself by killing the attacking rat, Jock along with Trusty has seen that Tramp is not all that bad of a dog. Jock felt extremely stupid and ashamed for misjudging Tramp badly.
Jock and Trusty rush to the dogcatcher's vehicle and attempt to stop it. Although they do, Trusty is apparently killed by the crash. Jock attempts to help but it seems there is no use. Jock then howls and mourns for his seemingly departed friend. That Christmas, Jock joins Lady along with her husband Tramp and four puppies. Despite Scamp, Lady's only son, tearing up his plaid sweater, he remains calm and congratulates Lady and Tramp on their kids, also noting Tramp's collar. As for Trusty, it seems it was only a broken leg and attends the Christmas celebration as well.
Jock makes a cameo appearance in the classic film during the famous Twilight Bark sequence.
He also makes a cameo to help the main pups get back to the farm in the first episode of the spin-off TV series.
Jock reappears in the sequel. He first appears alongside Trusty as they watch happily as 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. Jock and Trusty 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 where he joins an all dog band singing "Everybody Wants to Be a Woof". Later, he is seen amongst them as they chase away Pete.
- The word "Jock" is a definition of a male athlete.
- Jock's appearance is similar to Solo from the 1980 animated film Scruffy.
- Jock initially hated mongrels and strays such as Tramp, but after learning that Tramp saved the couple's baby from a deadly rat, Jock risked his own life to rescue Tramp when he was dognapped.
- In Lady and the Tramp, Jock was played by the late actor Bill Thompson, who also voiced Mr. Smee, the secondary antagonist of Peter Pan.
- Jock's singing voice was Sterling Holloway, who was also the original voice of Winnie the Pooh, the main protagonist of the Winnie the Pooh franchise.
- In Lady and the Tramp II: Scamp's Adventure, Jock was played by Jeff Bennett, who also voiced Tramp and the Dogcatcher.
Characters: Lady | Tramp | Jock | Trusty | Aunt Sarah | Si and Am | Jim Dear | Darling | Jim Jr. | Tony | Joe | Policeman | Professor | The Dogcatcher | Stray Dogs | Al the Alligator | Hyena | Mr. Busy | The Rat | Peg | Bull | Toughy | Boris | Pedro | Dachsie | Scamp | Angel | Annette, Danielle and Collette | Buster | Reggie | Francois | Sparky | Mooch | Ruby | Scratchy
Songs: Bella Notte | Jock's Song | What is a Baby? | La La Lu | The Siamese Cat Song | He's a Tramp | Welcome Home | World Without Fences | Junkyard Society Rag | I Didn't Know That I Could Feel This Way | Always There