croup rcoup corup ocrup rocup orcup cruop rcuop curop ucrop rucop urcop courp ocurp cuorp ucorp oucrp uocrp roucp orucp ruocp urocp ourcp uorcp cropu rcopu corpu ocrpu rocpu orcpu crpou rcpou cprou pcrou rpcou prcou copru ocpru cporu pcoru opcru pocru ropcu orpcu rpocu procu oprcu porcu crupo rcupo curpo ucrpo rucpo urcpo crpuo rcpuo cpruo pcruo rpcuo prcuo cupro ucpro cpuro pcuro upcro pucro rupco urpco rpuco pruco uprco purco coupr ocupr cuopr ucopr oucpr uocpr copur ocpur cpour pcour opcur pocur cupor ucpor cpuor pcuor upcor pucor oupcr uopcr opucr poucr upocr puocr roupc orupc ruopc uropc ourpc uorpc ropuc orpuc rpouc prouc opruc poruc rupoc urpoc rpuoc pruoc uproc puroc ouprc uoprc opurc pourc uporc puorc
Note: these 'words' (valid or invalid) are all the permutations of the word croup. These words are obtained by scrambling the letters in croup.