Kate Middleton is a self-proclaimed tennis fan, and it certainly showed during her latest appearance in London. On Tuesday, the royal, who is currently pregnant with her third child, served up some serious fun as she visited the Lawn Tennis Association at the National Tennis Center. Sporting a fashionable black tracksuit and sneakers, Kate couldn't contain her laughter as she tossed the ball around with some kids on the court. She even gave one boy a congratulatory high five after their one-on-one. Once again, she has proven that she's not too "princessy" to play sports, and we love it.