Grubbage was a large, fat, mostly deaf wharf rat in the motley crew of the Seascab. He was, according to Malbun Grimp, jolly and likeable, and an excellent navigator.
Due to missing both ears, Grubbage often misunderstood what his crewmates said (a fact that constantly irritated his captain, Plugg Firetail, and provided comic relief). However, he generally figured out any commands a little while later. He was the bosun aboard the Seascab, and apparently the steersrat too. He was captured by the Redwallers in Mossflower Woods near Brockhall. However, they liked him, and he was taken into Redwall Abbey. He was also used to navigate Triss and her friends to Riftgard, after which he presumably returned to Redwall. There he was popular and liked by all; it is presumed he stayed there until the end of his days.