Tubby Tumblemouse was one of Geronimo's bootcamp buddy's in Four Mice Deep in the Jungle. He said that he was a cheese salesmouse but he put on too many extra pounds eating cheese samples and Penolope Poisonfur sweet - talked him into taking her bootcamp course, saying it would be like a 'mini vacation.' Tubby's nickname was Furball and he seemed willing enough to share his emergency hidden cheese sandwiches with Geronimo so he seemed nice enough. Tubby Tumblemouse was overweight and he couldn't resist eating one of his hidden cheese sandwiches and Miss Penelope Poisonfur (A.K.A. P.P.) caught him and chucked the whole stock into the river. Penelope's nicknames for him include 'Tubster' and 'Tubby tail.' Apparently Tubby can't swim as Geronimo had to save him when he fell into a river. He thanked him by saying by the end, "If it weren't for you, I'd be at the bottom of a river!". On one page in the book he quotes: "I will never forget you Geronimo," with tears in his eyes after Geronimo gave him his snail burger.