Any time you're involved in research that involves Animal Testing it's generally a bad idea to get too attached to your test animals. Most of the time your experiment will end with these animals being killed and dissected (and not always ...In That Order).
However often in fiction this little detail is ignored and scientists are shown treating their test animals like pets, naming them and even playing with them or petting them. If the animal dies it is a freak accident and the scientist involved is usually filled with remorse.
Occasionally a work will invert this trope: a character will take a beloved pet and use it for experimentation. Often this can be used to show what a heartless Jerkass the character is, or that the character will simply do anything For Science!
- In Cowboy Bebop, Ein is a former lab animal called a "data dog", a Welsh Corgi which somehow has had its intelligence enhanced. It is stolen from the laboratory, and eventually ends up as the Bebop pet and mascot, and friend to Ed.
- According to the opening cartoon in Who Framed Roger Rabbit, Roger was formerly a lab animal.
- Dr. Brundle is much too attached to his baboons in The Fly (1986). This leaves him quite distraught when he turns one inside out.
- In The Amazing Spider-Man, Dr. Connors names his lab rats Fred and Wilma. At no point is a dissection considered.
- In Rise of the Planet of the Apes, Ceasar, the son of a lab chimp, is taken home and made a pet.
- Star Trek (2009): Inverted. Admiral Archer allows his pet beagle to be used in a teleportation experiment... with unfortunate results. (Word of God has it that this will likely be a Brick Joke later in the film series.)
- Night of the Lepus has this as its set up: the Scientist's daughter has grown attached to one of the test rabbits, and she swaps him with one from the control group. When said rabbit escape, it leads to the invasion of the Giant Killer Bunny Rabbits.
- Splice zig-zags with this trope, with the scientists constantly shifting between treating Dren as a test subject, a pet, an adoptive child, and a lover when he/she takes on an adult human appearance.
- In Project X, a researcher becomes a little too attached to a chimp that is about to be killed in an experiment. It turns out that the chimp knows sign language and bonds with the researcher.
- In the 2001 family film, Race To Space, Billy, the son of a NASA scientist, befriends one of the chimps being trained for space missions.
- From the Earth to the Moon has a 19th century inversion: in order to test whether the rocket's living compartment is secure, several animals are put inside including a cat and a pet squirrel belonging to one of the Gun Club. A week later, the compartment is opened, but the squirrel has evidently been eaten by the cat. The distraught owner wants to put its name on a monument as a martyr for science.
- The bunnies in The Secret World of Alex Mack are named and are never killed or dissected, not surprising as it is a children's show.
- In an episode of Quantum Leap Sam leaps into a lab chimp in the space exploration lab, being prepared to go into space. His experimenter gets attached to him, and complains when he's transferred to helmet testing - which is basically "put a helmet on a chimp and bash its head with a giant hammer."
- In the Cheers episode "Take Me Out of the Ball Game", the psychiatrist Lilith Sternin Crane has a pet lab rat named Whiskers.
- There's a Frasier episode in which it's revealed that Frasier's mother was so attached to her lab rats that she named her children after them.
- In one episode of Mighty Morphin' Power Rangers, Billy has a little white lab rat named Jack that he calls his "lab assistant".
- Inverted in House: House captures a wild rat in a co-worker's home, and decides to keep it as a pet, naming it "Steve McQueen". It is later indicated that he occasionally uses the rat for medical experiments.
- On Beakman's World, Lester is ostensibly the resident lab rat. However, the show is Post Modern enough to ignore this most of the time and treat him merely as what he is in real life: a guy in a rat suit. A few episodes even admit that he's an actor playing a "lab rat" role on a kids' science show.
- Cannon: In "To Kill a Guinea Pig", a medical researcher has adopted a former lab research monkey as a pet. However, mobsters kill it as a Dead Animal Warning to her.
- Our Miss Brooks: Mr. Boynton has a habit of naming many of his lab animals. However, that doesn't prevent him from doing fatal tests on them. In "New Girl in Town", it's revealed that he has been burying his mouse martyrs to science in the athletic field. Moreover, Miss Brooks has been (reluctantly) helping him. Averted in the case of Mr. Boynton's pet frog Mcdougall: although Mac is usually kept in the lab, he's a personal pet and not used for testing. Usually Mac's kept in a separate cage. However in the theatrical series finale, Mr. Boynton seems to have temporarily placed Mcdougall with a number of other frogs.
- An inversion: Doctor Borous in the Fallout: New Vegas add-on Old World Blues gave his dog Gabe, the closest thing in the world he had to a friend, as a subject for cyberdog enhancement research. If you complete a certain side-quest and present him with Gabe's dogbowl, he will have a My God, What Have I Done? moment over this.
- In Half-Life 2, Kleiner has Lamarr, a pet headcrab.
- The Amazing Spider-Man has Dr. Conners' Iguana, who was unknowingly exposed to some cross-species experimentation. When Conners was sent away to Beloit Mental Hospital, his iguana has mutated to human-size and then breaks out with the other cross-species very early in the video game.
- Inverted in Neopets, which allows you to acquire a "lab ray" after completing a secret laboratory map. You may then zap your neopets (now dubbed "lab rats") with the ray, causing random changes in size, gender, color and species.
- The Medic's doves from Team Fortress 2 are never used in any of his experiments, but they do hang around the lab. One of the birds, named Archimedes, has a habit of tunneling through the innards of the patient Medic is currently working on.
- Splatoon's feline judge Judd is implied to have been this to his former owner, the Professor. His unusual fur pattern and intelligence, coupled with the fact that his owner is known to have been a brilliant scientist, suggest that Judd may be the product of some sort of experimentation. Furthermore, when land-dwelling creatures faced extinction due to rising sea levels, the Professor cryogenically sealed Judd away for 12,000 years — as Splatoon 2 reveals, the capsule Judd was sealed in is also capable of cloning him.
- Doctor Steel is shown in two of his videos keeping lab hamsters as pets. One dies, giving him a moment of grief. While he's shown as being fond of them as pets, he's apparently not too attached to them (either that or he's not very good at naming pets); the second one seen has the imaginative name "Hamster 65".
- In The Powerpuff Girls (1998), Mojo Jojo started out as the professor's lab pet.
- Averted in an episode of The Simpsons, when Bart cons his way into a school for the gifted he is told not to get attached to the class hamsters as they are scheduled for dissection.
- In the short-lived Warner Bros. series, Pinky, Elmyra & the Brain, Elmyra from Tiny Toon Adventures acquires Pinky and the Brain as pets when Acme Labs goes bankrupt.
- Adventure Time: Princess Bubblegum has a lab rat named "Science" who she not only treats like a pet, despite being involved in some of her experiments, but is also trained to actually perform some complex experiments for her.
- On Rocko's Modern Life, Bev adopts a pit bull named Earl that had escaped from the science lab. Her husband sends poor Earl off into space, in an attempt to get rid of him, but two Starfish Aliens return him to Bev.
- On Rugrats, Chuckie is given a new allergy treatment, which works for a while, but proves to be only a temporary solution. To make up for it, the allergist lets him keep her lab mouse, "Cheddar."
- Modern pet golden hamsters, fancy rats, and fancy mice were derived from laboratory stock. Bred in captivity to make them docile research subjects, these rodents lost their natural aggression and much of their fear of humans, making them better pets.
- Many Real Life experiments in animal behavior or learning processes actually require this trope be in effect, as it's necessary to establish enough of a rapport with the animal so it won't be too afraid of the researchers to complete its tasks. So long as the control group is treated identically, letting a research animal become friendly to its keepers needn't be a liability in non-injurious experiments.