My parents called me to tell me my sister had had the baby, so I went to the hospital later that day to see her. My parents had gone to the gift shop or something so it was just her and I in the room - maybe her husband, too. The baby wasn't in the room and my sister didn't look all that different to me so the conversation was like this.

Me: I thought mom said you had the baby already.
Her: I did.
Me: But....(said really confused)
Her: Get the yewt out of here, right now!!!

Still not funny to her.