Ty/Marcy had with her power had found that one of the neighbors kid name Jeff had been taking and being mean to his dog that had been fixed. He then turned the boys testicles into a dogs testicles then he switched the boy and the dogs reproductive area around. So now the boy hadn't a ball-sac.
Ty/Marcy then decided that since the boy liked to beat on dogs that he would make it so that the boy would now have in place of his penis and empty sac that the boy would have a female dog's reproductive organs. He then made it so that his new female dog vagina was in he.
Ty/Marcy had also made it so that each time he went into heat that any male dog or even human would mount and screw him. Jeff would gain another aspect of a dog.