"Henry's bagina is funny, mama."
Big breath in -
"Henry does not have a vagina, Willa. Henry has a penis."
"A peeeeeeee-nis?!" [insane sugar-hyped laughter] "that's silly!"
"Boys have a penis and girls have a vagina."
"I have a bagina, mama. You too."
Then she listed every person she ever met, and guessed their gender anatomy with good accuracy. This took a good 20 minutes. I can't wait to hear a report from her teacher this afternoon.