For some reason I just remembered my brother and I's version of "playing doctor." It was called "Take Apart the Captain" and it consisted of one party slowly and painfully dismembering the other.
"Sorry, Captain, I'm going to have to cut off your leg."
"No no, please don't cut off my leg."
"Sorry, I have to cut it off. Here's my circle saw. BRRRRRR."
"Ouch, please, God, the PAIN!"
All of our body parts would be amputated one by one until we were "just a big vagina running around" (or a big penis)- at which point we would laugh hysterically, switch roles, and do it all over again.