Who Watches The Watchmen?

(I work in a candy shop at an airport. I ring up an English-speaking customer, by his looks a middle aged business man, who bought himself some sweets for the flight. When I put his items in a bag, this happened.)

Customer: “I’m watching you.” *smiling*

Me: *baffled* “Uhm… Excuse me?”

Customer: “I’m watching you!”

(I have no idea what he wants and it’s really awkward and creepy. Suddenly he’s shocked:)

Customer: “Oh, no, no, no! That sounded really creepy, didn’t it? Oh, my god! It says so on your shirt and I thought it was funny!”

(I look down. I’m wearing a shirt with a cute bat with big eyes. Next to it, “I’m watching you” is printed in big letters.)

Me: “Oh, I really didn’t realize I’m wearing this shirt! I’m so sorry!”

(We laughed and he left. I didn’t wear that shirt for work again.)