Haven't you ever wanted to throatfuck someone through their ass? Just tell them to take some anti-acid so your dick doesn't burn in their stomach and you're good to go.
When the MC was fucking one of the girls' lungs, I quit. Why not just make his dick a little bigger and have the girl giving him a blowjob through her pussy?
Truth or dare scenes. If the mc is in the same room with a family member and at least one female friend, sooner or later they'll decide to play truth or dare.