One assumes this refers to "poo" poo as opposed to "winnie the" poo[h] in which case the bear and the rabbit were both having a poo and the bear asked the rabbit "how do you keep so clean?", the rabbit answered "I have a sort of oil in my fur which prevents any 'dirt' clinging to it". "That's handy" said the bear and promptly picked up the rabbit and wiped his own ass with it.