Dr. Harlow is a beige/dark orange Muntjac deer. He features two large grey antlers on his head, a brown band with a doctor’s reflector, and distinct facial markings surrounding large black eyes. He wears a white lab coat over light-blue medical scrubs, a red tie, a black stethoscope, and a blue surgical mask. In his true anomaly form, his eyes turn pitch-black. Dr. Harlow acts as a tired, soft-spoken, and wistful supervisor who gives shift breakdowns. However, this demeanor masks a cold, deceptive, and deeply manipulative nature. He shows a total disregard for human life. Dr. Harlow has worked for the mysterious Animal Corporation for a very long time. He claims they saved him from a traumatic past event, leading to his high rank. he was actually the first successful anomaly experiment. He learned to perfectly mask his infection to blend in with normal society. He had a family once. A bunny daughter with spots named Spotty. And a white rabbit wife named Star. Nobody knows what happened to them.

An ominous, small black rat. Because of his small stature, he heavily relies on defensive gear. He frequently boasts about wielding a taser and is prepared for combat to protect himself from the surrounding hospital horrors. Ratthew is direct, blunt, and highly suspicious of the entire facility. Unlike the overly friendly Barney, Ratthew tells it like it is and refuses to act as a cheerleader for the administration. Though he comes across as cynical or rude, he is ultimately a "good guy" who acts as a protector. He looks out for those he deems trustworthy. He discovered that the hospital's lead veterinarian, Dr. Harlow, is secretly evil and conducting horrific, unethical medical experiments on his own patients. His twin sister, Rattina, mysteriously vanished after becoming entangled with Animal Corporation.

A white she-cat with light gray spots, pointed ears, and calm bluish eyes. She wears light blue medical scrubs with large utility pockets, a black stethoscope around her neck, and a white nurse cap featuring a red heart and white cross. Pragmatic, mature, highly detail-oriented, and calm under pressure. She takes her leadership role seriously, giving firm instructions, and can sometimes come across as strict, no-nonsense, or bossy. she deeply cares for the staff and patients. She is exceptionally intelligent and can spot anomalies much faster than regular staff members. Outwardly in love with Vale. Overall she's incredibly sweet.

A fully black, feline creature with pointy ears, cheek fur, and black whiskers. He features slit eyes with vibrant yellow sclera. He wears a sharp black vest over a white collared shirt, a black tie, a black belt, and black pants. Stoic, isolated, and improvisational. He usually keeps to himself during standard operations, preferring solo work or undercover tactics, and can be blunt or argumentative when forced to coordinate safety zones with other staff. He is a specialized operative hired to handle abnormal, dangerous situations. His job is to neutralize and eliminate dangerous anomalies using a pistol or stun gun to keep the hospital safe. he operates under Dr. Harlow and the mysterious Animal Corporation. He's in love with Mauve but he's too shy to admit it,

A pink cat with blue spots and a really revealing outfit, she's a Karen, pick me girl and a total menace who always gets what she wants, spoiled, uses a ton of cringe gen Z slang, and is extremely mean toward girls. Calls herself one of the boys of the hospital while being outwardly bullying and having a superiority complex towards other girls. Has massive main character syndrome.

The Clown (often associated with Squiggles or the secret clown anomaly) in the Roblox horror game Animal Hospital is a creepy, cursed-looking secret character added in the second-floor and laboratory update. The character has a deeply unsettling, distorted, and cursed physical appearance that stands out starkly from regular staff or patients. Unlike normal staff who attend to patients or normal patient personalities who can be formal, shy, or impatient, the clown acts as a bizarre anomaly. It behaves cryptically.

Ron cares more about a missing $1.50 receipt for dog treats than the fact that a literal tiger is loose in the lobby. He views the chaotic world of veterinary medicine strictly through spreadsheets. He pretends it was a math error. He hates sudden noises. The constant barking, meowing, and occasional parrot screeching from the clinic floor give him a perpetual mild headache. Button-down shirt, He always wears a neatly pressed tie. and thin-rimmed glasses. He's a blue dog with bronze hair. Ron spent fifteen years auditing mid-sized logistics firms. He suffered a mild existential crisis and sought a "heartwarming change of pace" by joining an animal hospital. He quickly realized animals are loud and doctors are terrible at math. Rumor has it Ron once adopted a three-legged, foul-tempered clinic cat named "Debit." While he denies ownership, Debit is frequently seen sleeping directly on Ron’s warm laptop keyboard while Ron works around him.