Preheat oven to 400 degrees F. Cut the mozzarella sticks in half. If they are too hard to cut then thaw them just a little in the microwave (about 10 seconds). Wrap each half of the mozzarella sticks with one half of a strip of bacon. Repeat until all mozzarella sticks are wrapped with the bacon. Place the wrapped sticks on a baking sheet and bake for around 15 minutes. Do not let the bacon burn! The mozzarella may ooze out a bit so let them cool for 5 minutes after taking them out of the oven and use a spatula to scrape them up cleanly.
To serve: Use toothpicks inserted into one piece of the pineapple then inserted into the bacon bites. Serve them with the toothpicks in, but be careful with little children eating these because of the toothpick.
Serve with marinara sauce if desired.