carks acrks craks rcaks arcks racks cakrs ackrs ckars kcars akcrs kacrs crkas rckas ckras kcras rkcas krcas arkcs rakcs akrcs karcs rkacs kracs carsk acrsk crask rcask arcsk racsk casrk acsrk csark scark ascrk sacrk crsak rcsak csrak scrak rscak srcak arsck rasck asrck sarck rsack srack caksr acksr ckasr kcasr akcsr kacsr caskr acskr csakr scakr asckr sackr cksar kcsar cskar sckar kscar skcar akscr kascr askcr sakcr ksacr skacr crksa rcksa ckrsa kcrsa rkcsa krcsa crska rcska csrka scrka rscka srcka cksra kcsra cskra sckra kscra skcra rksca krsca rskca srkca ksrca skrca arksc raksc akrsc karsc rkasc krasc arskc raskc asrkc sarkc rsakc srakc aksrc kasrc askrc sakrc ksarc skarc rksac krsac rskac srkac ksrac skrac
Note: these 'words' (valid or invalid) are all the permutations of the word carks. These words are obtained by scrambling the letters in carks.