How do we keep a straight face?

Julia is still being very stubborn about potty training. So tonight she and Chris had been on the couch watching Tinkerbelle. I came up from downstairs, and she is on the floor being changed, and she asked Chris if he was mad at her. He told her he was so I asked what happened. She had peed thru her Pull-Up and got the couch wet so he was aggravated. So I said to Julia with an agitated tone, "Julia when are you going to stop being a baby and go on the potty?"

Her response, "I get bigger on Monday, Mommy."

LOL!