I've done this as an adult. They got mad but I just ignored it and said "are you going to check me out" and they did.

Tangentially related. In college or football team would go to old country buffet. Which has a microphone in the wall to order more from the kitchen for the staff. One of our smart ass players went up and said "we need more fried chicken". The manager caught him and scolded him. Then looked at the buffet and said "make that two orders of fried chicken" in the mic.