Grumps is a hellcat found southeast of Aubury's Rune Shop in New Varrock. He demands Gertude's pet sardine. He is one of four cats, along with 'Fraidy cat, Baron Mauser and Catbot 9000 that the player needs to shoo away for "The Cats Bane" task.
After the completion of the task "Cats Bane" he can be found at the graveyard on the west New Varrock bank trying to resurrect Fluffs. After Fluffs is revived, he may then be found in Gertrude's house.