Since the boy had his *father's* penis, it also meant he was producing his own father's sperm. This technically makes himself the father now, which resulted in them switching their genetic information and places and in the family tree.
George's penis started to pulse after a huge wave of testosterone was sent into his body. His body and more muscular until it matched his father's body, standing at 6'7". Then his father started crying when his body deflated, shrunk and practically lost all it's definition, now standing at 2'3".
George was definitely shocked that he is now a 23 year old man rather than a 2 year old boy. He said to Anthony: "Daddy! You're so short now, and you're crying like a baby!" Anthony felt very weird when his son called him daddy, as if he wasn't George's father at all.
The second change was their heads and faces; George's head became more of an egg shape, and his face changed into a much older and better looking face. Anthony, on the other hand had his head shrink to a smaller size and gain a childish face. The final change was the hair. It didn't take long for hair to appear all over George's body. He even had a beard. Meanwhile, Anthony now had hairless skin.
They swapped clothing and George put a diaper on his own father (Technically son) who is now two years old. "Daddy can we get my shoes now?" said Anthony in his new squeaky voice. It seems that their minds were altered and traits were switched. "Sure we can!" said George, in his new baritone voice.