A promise is a promise

Jon's mom slowly walked down the hall and placed the stone on the living room coffee table, and continued to clean the house. A few minutes later Megan, Jon's ten-year-old sister. She was just starting purverty. When she entered the living room and saw the rock. "Mommy!" she called.
"What?" her mom called from the kitchen. "I'm kind of busy!"
"Were did Jon go?" she asked.
"To the Mall I think, why?"
"He was going to help me with my costume for Katie's party"
"That will have to wait till he gets back."
"But the party's at three" she said looking at the clock that read noon.
"Sorry Megan sweaty, Jon will be home soon."
"Ok" Megan said sitting down and seeing the rock. 'What's this?' she thought picking up the stone. "I wish I knew were this stone came from." In flash Megan knew all bout the stone and were it came from. A smile crept across her face.
Later around One Jon and Karen arrived home to see Megan sitting on the floor on Jon's room with costumes that she wore in the past strung across the room.
"Megan! What the hell are you doing?" Jon yelled.
Megan just smiled "You said you would help me with my costume."
Jon paused "What?" he said puzzled.
"My Costume, for Katie's party, remember?" Megan said coyly
"No, now get out of my room!" Jon yelled.
Megan looked up and smiled pulling the stone from her pocket. Jon's eyes grew big. "I wish you would help me with my costume." she pause, "Not just any way but for him to me a girl my age!" she wished.
Jon felt a sight tingle as the stone began to work it's magic.