Bubble

While sitting in the car waiting for the rain to subside a bit before dashing into the grocery store, I let Amy come up front.
"Mommy," she asked. "Where's the bubble?"
"I don't have any bubbles in the car," I replied, thinking she was talking about some bubbles I gave them earlier.
"No, Mommy," she insisted. "The bubble that could hurt me if I sit up front."
Now I'm thoroughly confused. "I've no idea what you are talking about!" I admitted.
"You know mommy, the bubble that comes out if the car crashes. You said it could hurt us." Amy explained.
"Oh," I laughed. "You mean AIR BAG?"
"Yes," Amy sighed. "Where is that bubble?"