Slice the top off the tomatoes, reserving lids. Scoop out seeds from each tomato.
Microwave rice according to on pack instructions, and stir tuna through rice to combine. Spoon warm rice mixture evenly between four tomatoes, and place lid of tomato loosely on top to close.
Place two olives at the top of each tomato, to make the eyes.
Cut each piece of bocconcini into three pieces. Place one below the olives, to make a mouth. Place the remaining two pieces at the base, to make the feet.