 Stephen King (I) (qv) sold the rights to the movie very cheaply  out of his friendship with Frank Darabont (qv). They had  originally become friends when Darabont adapted a short story of  Kings called "The Woman in the Room" (King has a policy stating  that any aspiring filmmaker can adapt his short stories for a buck)  and King was thoroughly impressed. They maintained a pen pal  relationship and didnt actually meet until Darabont optioned  Shawshank.