upby puby ubpy bupy pbuy bpuy upyb puyb uypb yupb pyub ypub ubyp buyp uybp yubp byup ybup pbyu bpyu pybu ypbu bypu ybpu
Note: these 'words' (valid or invalid) are all the permutations of the word upby. These words are obtained by scrambling the letters in upby.