[Whilst changing his diaper at bed time.]
Him: Jammies off!
Me: Yep, we're taking off your jammies.
Him: Diaper off!
Me: That's right, we're taking off your diaper and putting on a clean one.
Him: Penis off!
Me: No, the penis stays on.
Him: Bye-bye penis!
Me: No, you're keeping the penis. At least until you're older and have had years of therapy and extensive hormone treatment.