Impregnate him

You feel yourself about to cum.

"Alright daddy, time for you to take your son's load."

"Give it to me." your father moaned. You felt it build up inside you and you thrust deep inside him. Your mind is full of images of filling him with your cum, breeding him, and how much of a pussy he was. The dark mist enshrouds the both of you. You shoot deep inside, and it feels like your dick is a hose. Cum began spilling out, his stomach was lifting, the cum filling him up. You slide your dick out slowly and look down at your father. He is lying in a pool of your cum, giggling, legs sprawled in the air. You go wipe to some of the cum covering his asshole, when you reveal a vagina?!?

"Dad? What happened to your asshole?" you look at your dad, who is no longer giggling, but instead clutching his cum filled tummy.

"ungh I don't feel so good." he bucked his hips