Greebo is a cat in Terry Pratchett's Discworld books. He is first introduced in Wyrd Sisters. He is a foul-tempered one-eyed grey tomcat whose human, Nanny Ogg, insists against all the evidence that he is a sweet, harmless kitten. In the course of the books, he has killed two vampires, eating at least one of them in the novel Witches Abroad:
- The bat squirmed under his claw. It seemed to Greebo's small cat brain that it was trying to change its shape, and he wasn't having any of that from a mouse with wings on.
- Greebo had spent an irritating two minutes in that box. Technically, a cat locked in a box may be alive or it may be dead. You never know until you look. In fact, the mere act of opening the box will determine the state of the cat, although in this case there were three determinate states the cat could be in: these being Alive, Dead, and Bloody Furious.
- Shawn dived sideways as Greebo went off like a Claymore mine.
- "Don't worry about him," said Magrat dreamily, as the elf flailed at the maddened cat. "He's just a big softy."
In Witches Abroad he was transformed, for reasons that seemed to be a good idea at the time, into a human. He was confused by the differences between human and cat morphology and social relationships, but picked some aspects up quickly. In this incarnation, the character is reminiscent of Red Dwarf's Cat; he looks like a 'beautiful, brainless bully' who has raided a leather goods store for the discerning pirate, and appears ready to unbuckle any amount of swash, radiating an aura of raw sex that can be felt several rooms away, and of a Megawatt magnitude. He is typically covered in scars, has retractable nails (or more accurately, claws) and maintains a slitted left eye. He still retains feline behaviour in this human form such as the inability to work door handles and using his own saliva to clean himself.
The incident left him with an unstable phenotype, that is, a tendency to temporarily switch forms when completely cornered, which causes some excitement. In Maskerade he once more took longer-term human shape, attending the Ankh-Morpork Opera in the guise of the Count Gribeau.
In a passing reference in Witches Abroad Nanny Ogg said that Greebo was a demon ("Just between you and me, he's a fiend from hell"), possibly indicating that Greebo is indeed demonic, partially due to Nanny's insistence otherwise that Greebo is a gentle kitten. In addition to his other qualities, he is pursuing a study in inbreeding with all of the other cats in Lancre that are related to him (which by dint of some effort is all of them, as he is currently every male ancestor for at least 30 generation), which may be involved in the "raw sex" aura he possesses mentioned above. He has also seriously surprised a she-bear (also killed and eaten half of one before) and chased a female wolf up a tree.
To date, Greebo is known to fear only three things:
- the Nac Mac Feegle
- the black cockerel Legba, who belongs to the voodoo 'witch' Mrs Gogol
- 'You', a small white kitten owned by Granny Weatherwax. Their first encounter ended with You burying her claws in Greebo's face and his subsequent retreat. He now hides behind the pots and pans whenever she is in the same house as him.
In Terry Pratchett's Johnny Maxwell series, Mrs. Tachyon owns a cat named Guilty who has many qualities similar to Greebo.