Exactly What It Says on the Tin: a pet animal who steals things. Often, but not always, they then stash them away in a Treasure Room (or doghouse). This trope applies when the pet steals with the intent to keep the item—simply engaging in a playful tug-of-war or a chase with the intention of being caught does not count.
This can lead to Mistaken for Thief if someone is thought to have stolen something that was actually stolen by a pet.
Often seen in Kid Detective stories.
A variant is a pet owned by a thief which has been specifically trained for the task.
Can be Truth in Television.
- In Clue Jr.: The Case of the Missing Toys, the dog, the rabbit, the bird, the cat, or the fish stole the titular missing toy and hid it in the clubhouse.
- In Gotham Academy, Ham the dog has a collection of odds and ends from various students in a hole under one of the buildings.
- In Knights of the Dinner Table, B.J. Felton's 50 pound neutered cat named Colonel Prowler has stolen many dice, miniatures and other items over the years and stored them in his bedding.
- Abu, the monkey sidekick of the titular Aladdin, is a kleptomaniac who nearly gets himself, Aladdin, and Carpet killed by stealing something from the cave of wonders.
- One of the subplots in Titanic: The Legend Goes On involves a raven stealing Angelica's beloved locket, and the ensuing hunt to get it back from the woman he gave it to.
- National Lampoon's Dorm Daze 2: Semester @ Sea features a monkey that frequently steals items, including the Pharaoh Diamond.
- In the Fantastic Beasts series, Newt Scamander's Niffler is constantly trying to take shiny things. This ends up coming in handy in the second movie, as it steals the blood pact Dumbledore made with Grindelwald, meaning that Dumbledore now has a chance to destroy it and move against Grindelwald directly.
- In The Nose Knows, a neighborhood dog ends up with the missing glove as well as many other missing items from the neighborhood in his doghouse.
- In The Doll People, one of the dolls' fears is being taken by the family cat The Captain, who will snatch them in his mouth if given the chance.
- In Slinky Malinky, the titular cat, who lives in a house, steals from the neighbors.
- In the Milly, Molly book "Sock Heaven," Milly's dad's sock goes missing and it turns out that Marmalade the cat stole it.
- In The Brady Bunch episode "Kitty Karry-All Is Missing," Cindy suspects Bobby of stealing the titular doll. Eventually, they figure out that family dog Tiger was the thief.
- Community: Troy's monkey Annie's Boobs steals things around the college and hides them inside the air vents.
- One winning video on America's Funniest Home Videos, entitled "Cinemadographer", was unintentionally filmed by a dog when it stole a camcorder.
- In Pokémon, Purrloin is a cute little kittycat known for stealing things.
- In The Legend of Zelda: Majora's Mask, the Takkuri steals items and delivers them to the man who runs the black market shop in Clock Town.
- In Nethack, your pet can be trained to steal from shops, with no repercussions.
- The third episode of Phoenix Wright: Ace Attorney - Justice for All, "Turnabout Big Top" takes place at a circus, where one of the animals there is Money the Monkey. Money has a habit of stealing shiny things, as Phoenix found out when the monkey stole his attorney's badge. Of course, the monkey ends up a key factor in the events surrounding the ringmaster's murder. When Money steals something, he takes it back his home, which happens to be the room of Acro the Acrobat, who at the end be exposed as the ringmaster's murderer. As Money is a strong monkey, one of the items he stole was a life-sized bust of the suspect, which Acro would end up using as the murder weapon.
- In the Martha Speaks episode "Martha's Life in Crime", it's revealed that before Martha was adopted, two thieves tried to adopt her and train her to steal, but it didn't work out.
- One Handy Manny episode revolves around a woman's new dog taking her socks.
- One episode of Scooby-Doo! Mystery Incorporated features a monkey that was trained by it's owner to steal things like money and jewelry at the ring of a bell. It worked perfectly until the monkey eventually started bringing back bells with the valuables and then only bells and whatever was attached to them instead of the intended targets.
- In 2010, a Portswood, UK house cat named Oscar made the news for stealing panties.
- Several YouTube videos feature pets stealing.
- Anyone who has ever owned a ferret can attest to this. If it's not nailed down, the ferret will make off with it and try to stash it in their hiding place (even if it doesn't fit). In fact it's right there in their name: Ferret derives from Latin furittus, or "Little Thief."