The knot popped out of Zack's penis, but to his confusion, the thread kept coming. At least it was coming out smoothly now. It didn't look special, kind of off white, maybe flesh colored, and felt smooth enough. The thread seemed to loop around inside him, like a spool unraveling up and down his dick.
Then, when the sensation reached his tip... it started to unravel by itself. His eyes bugged out as he watched the tip of his penis unravel and instantly stopped, pinching it in place. The rest of his penis still felt fleshy but the tip which was now thread didn't feel like it was apart of him, and it just felt like a kind of cold bit of fabric.
He tried to push the thread back onto his dick but it wouldn't stick or go back in. He dropped the thread on accident and lost another inch of length, but he quickly caught it before he lost anymore. Wide eyed, Zack carried his dick thread as he stood up and looked in the mirror. He wasn't angry or sad just.. puzzled. What the hell was going on?
As if in answer to his question, the doorbell rang. He swore.. carefully rolling up the thread and stuffing it in his foreskin. Zack pulled his pants up, and his underwear up as tight as he could get it, and then opened his front door.