Taylor Swift & Calvin Harris -- Dessert For 3

If you're gonna crash Taylor Swift and Calvin Harris' romantic dinner date ... this is the way to do it.

The couple's table for 2 at Giorgio Baldi in Santa Monica Tuesday night turned into a table for 3 after a young fan sat in with them during the meal.

The kid managed to get a photo with Taylor and Calvin, and then hilariously roasted them with the caption: "Awesome dinner with mom and dad."