The tradition comes from Ireland and the original lanterns were made from Turnips or Potatoes (pumpkins began to be used once the tradition moved to america).
To plant a pumpkin or watermelon seed you should place them inside a wet paper towel and then seal it up in a Ziplock bag. You should wait a few days until you see seedlings. Transfer seedlings into potted soil, water, and plenty of sun light.
pinneapple, and tomatoes
Sadly, you cannot... If you want a fruity chia however, you can always go get a magical chia-pop.