Your what did what?

Last night I was at book club and Joker was home alone with the Bug. The following anecdote was thus relayed to me second-hand, but it was so funny I'm sharing it anyway.

So the Bug was in a delightful mood all evening, particularly during bath time. She did not want to get out. At all. So Joker drained the tub figuring that would cause it to lose some of the allure. Not so much. The Bug sat there laughing and kicking her feet on the rubber sticky mat. The mat shifted a little and let out a funny squeaky sound which startled the Bug. She looked up at Joker, down at the mat, and came to her conclusion. "Dada, my vagina burped!"