Chuck was a bully. Nobody liked him. He bragged about his sexuality but no one, neither male or female, would have anything to do with him. He was just a jerk.
You managed to get some hair from him the day before and now you were ready. It was math class, the most boring class of the day and you had your voodoo doll hidden under the desk. You planned out ahead of time exactly what you would do.
First you touched the quartz crystal to the voodoo doll's crotch. Chuck suddenly sat up straight as he felt a jolt of energy in his pants. You continued rubbing and Chuck's face reddened. You then grabbed the crotch of the voodoo doll and pulled knowing that would cause Chuck's cock to grow. You kept pulling until Chuck's cock peeked out of the top of his pants.
The teacher said, "Chuck, will you come up to the front of the class?"
Chuck grabbed his book and covered himself but everyone including the teacher quickly figured out what he was covering.
The teacher asked, "Do you need to be excused."
Chuck mumbled, "Yes sir, may I go to the toilet please."
But you weren't done playing with Chuck. You squeezed the voodoo dolls arms causing Chuck's arms to shrink in both length and width. Before he made it out of the class, he was failing to keep his cock covered by his book. The class got a nice eyeful of Chuck's large erection.
But now that you could no longer see Chuck's embarrassment, you decided to change your tactic. You made Chuck's cock shrink until it was barely visible. By the time Chuck got to the toilet, he wouldn't be able to find his own cock and would have to sit to pee.
Then you found the voodoo doll's anus and started playing with it. You imagined that Chuck was whimpering now.
You decided to put the voodoo doll away for now. You'd tortured Chuck enough for now. If you wanted to see Chuck again, not cowering in a bathroom stall, you better ease up on him and let him attempt to compose himself. Maybe during Physical Education you could tease Chuck more and not give him a way to hide.