spark psark saprk asprk pasrk apsrk sprak psrak srpak rspak prsak rpsak sarpk asrpk srapk rsapk arspk raspk parsk aprsk prask rpask arpsk rapsk spakr psakr sapkr aspkr paskr apskr spkar pskar skpar kspar pksar kpsar sakpr askpr skapr ksapr akspr kaspr paksr apksr pkasr kpasr akpsr kapsr sprka psrka srpka rspka prska rpska spkra pskra skpra kspra pksra kpsra srkpa rskpa skrpa ksrpa rkspa krspa prksa rpksa pkrsa kprsa rkpsa krpsa sarkp asrkp srakp rsakp arskp raskp sakrp askrp skarp ksarp aksrp kasrp srkap rskap skrap ksrap rksap krsap arksp raksp akrsp karsp rkasp krasp parks aprks praks rpaks arpks rapks pakrs apkrs pkars kpars akprs kaprs prkas rpkas pkras kpras rkpas krpas arkps rakps akrps karps rkaps kraps
Note: these 'words' (valid or invalid) are all the permutations of the word spark. These words are obtained by scrambling the letters in spark.