Transgender Surgery

Yesterday morning Ava and Vivian and Evan played on the trampoline. Then they came over to play indoors. I overheard them talking.

Ava: "Vivian, do you know that with surgery a girl can become a boy?"
Vivian: "What?"
Evan: "And with surgery a boy can become a girl"
Vivian: "What is surgery?"
Ava: "I don't know"
Evan: "You can put boy parts on a girl to make a girl into a boy"
Ava: "And you can put girl parts on a boy"

Silence, while they ponder this.

Vivian: "And then you'll have to cut the boy's head and put a girl brain into it to change it into a girl"