Mugged Of Their Green Credentials

(There’s a coffee shop in the library on my college campus. There are signs advertising a school mug as a way to be more green, by using fewer paper cups. My friend goes there one day with one of these mugs.)

Friend: “I’d like a [coffee].”

Cashier: “That’ll be [price].”

Friend: *handing over payment card* “I have one of these [College] mugs. Do I give it to you to fill?”

Cashier: “Oh, no. You fill the mug yourself after we give you the drink in one of the paper cups.”