zurf uzrf zruf rzuf urzf ruzf zufr uzfr zfur fzur ufzr fuzr zrfu rzfu zfru fzru rfzu frzu urfz rufz ufrz furz rfuz fruz
Note: these 'words' (valid or invalid) are all the permutations of the word zurf. These words are obtained by scrambling the letters in zurf.