Putting The Brakes On This Conversation

(It’s a snowy Saturday morning. I am waiting in line, directly behind a young woman and her little boy, who looks to be about six years old. The cashier is being friendly with him, and he is telling her all about the toy that was just purchased for him. His mother tells him it’s time to go, and then:)

Cashier: “Have a great day and drive safely!”

Mom: “Have a nice day.”

Boy: “We WILL drive safely.” *pause* “Unless Mom goes like ‘aaaahh!’” *mimes looking shocked and stepping on the brakes*

Mom: “[Boy]!” *hastily rushes him out of the store as I snicker*