Eating Breakfast, Lunch, and Dinner at each of the restaurants you choose. This is quite a feat when you don't have a car and have to rely on your parents to drive you places.
"On my birthday I managed to pull off the HatTrick, I ate at Dunkin Donuts in the morning, Burger King at noon, and had breadsticks at Pizza Hut at dinner time."
The term probably originates from bridge, the card game. During game play, four cards are compared and the highest card wins the comparison. In the jargon of the game, each round of comparison is called a "trick". A hattrick involves winning three tricks, generally in a row, which pratically assures winning the current round of play.
John's holding three aces.
Well, that's an easy hattrick.