Greebo is also the name of Nanny Ogg's pet cat (from the Discworld series). Nanny, being the slightly dotty old matron that she is, still thinks of Greebo as a loveable little kitty cat (as she puts it, "He's an old softy, really"). Most other citizens of Lancre, however, think of Greebo as nothing but a ratty-eared, one-eyed, sex-crazed, homicidal, walking disaster area. He spends most of his days looking for things to kill, eat, rape, or perform some combination of the three on.

Greebo is possibly one of the toughest feline lifeforms in existance, capable of giving bears, wolves, and full-grown humans a run for their money. About the only things that have ever scared him were elves (in "Lords and Ladies"), the Nac Mac Feegle (in "Carpe Jugulum"), a voodoo fighting cock named Legba (in "Witches Abroad"), a mother fox defending her cubs, and Granny Weatherwax's kitten You (in "Wintersmith").

In "Witches Abroad", Greebo was turned into a human for a time, and since then has had a tendency to change into his human form (a ruggedly handsome man with an eyepatch, who is described as able to "commit sexual harassment by standing very quietly in the next room") under extreme duress. Since he often changes without any clothes on, this has caused some serious wackyness to ensue.