muff umff mfuf fmuf ufmf fumf muff umff mfuf fmuf ufmf fumf mffu fmfu mffu fmfu ffmu ffmu uffm fufm uffm fufm ffum ffum
Note: these 'words' (valid or invalid) are all the permutations of the word muff. These words are obtained by scrambling the letters in muff.