For fun themed snacks, my husband helped me make Mario Star Sandwiches. We made peanut butter and jelly sandwiches and cut the centers of them with a star-shaped cookie cutter. Then we buttered the back of two raisins and pressed them on the front of the sandwiches for the eyes of the Mario Star. They turned out really cute and the kids loved them! We were lucky not to have anyone with a peanut allergy but you could do this with any type sandwich.
I also had Mario Brothers fruit snacks to add to our theme. We had my son's other favorite foods too: chips & dip and a meat and cheese platter. It was super simple but still tied into the party theme. Perfect!