quack uqack qauck aquck uaqck auqck qucak uqcak qcuak cquak ucqak cuqak qacuk aqcuk qcauk cqauk acquk caquk uacqk aucqk ucaqk cuaqk acuqk cauqk quakc uqakc qaukc aqukc uaqkc auqkc qukac uqkac qkuac kquac ukqac kuqac qakuc aqkuc qkauc kqauc akquc kaquc uakqc aukqc ukaqc kuaqc akuqc kauqc qucka uqcka qcuka cquka ucqka cuqka qukca uqkca qkuca kquca ukqca kuqca qckua cqkua qkcua kqcua ckqua kcqua uckqa cukqa ukcqa kucqa ckuqa kcuqa qacku aqcku qcaku cqaku acqku caqku qakcu aqkcu qkacu kqacu akqcu kaqcu qckau cqkau qkcau kqcau ckqau kcqau ackqu cakqu akcqu kacqu ckaqu kcaqu uackq auckq ucakq cuakq acukq caukq uakcq aukcq ukacq kuacq akucq kaucq uckaq cukaq ukcaq kucaq ckuaq kcuaq ackuq cakuq akcuq kacuq ckauq kcauq
Note: these 'words' (valid or invalid) are all the permutations of the word quack. These words are obtained by scrambling the letters in quack.