"You're welcome, bottom"

Olivia has a problem with diaper rashes. She loves to go pee on the potty, when she feels like it. Yesterday she wanted a diaper. Ok, that's fine with me (I was feeling lazy anyway, and let's face it, potty training is a lot of work). So at the end of the day her bottom was suffering the consequences of her wetness. So, today is a new day, and I suggested underwear so her poor fanny could recuperate from yesterday.
This leads us to our brief, but hilarious conversation after lunch today:

"Olivia, I am so proud of you for wearing your undies today. Your bottom will thank you."
(Then I thought how funny it was that I said that, since a two year old doesn't usually understand such types of humor.)

Olivia walked away to go play, and I heard her say quietly, "You're welcome, bottom."