He picked up Dipper and trudged to his bedroom. He laid the boy on his bed.

Stan pulled out a long mirror. On the top it had a sun with a cavity in the middle. He flipped it over, and the other side had a moon with a same sized cavity. "Dip... I have to do something... and... I'm really sorry." Stan grabbed his break in kit and pulled out a knife. He stabbed it through the child, making Dipper poof away.

On the bed laid a gem. Dipper. Stan sighed and fit Dipper on the moon of the mirror.

(Then I realized that, gems can't retreat when their stone is cracked. So finding a potion it is.)