Make cake according to package directions. Spray a 9x13-inch baking pan
Slice and smash berries slightly to make some juice.
Mix dry jell-O into strawberries and juice.
Pour mixture into prepared pan.
Sprinkle marshmallows over berries
Pour cake batter over all evenly.
Bake at 350^ for 35 minutes or until cake tests done.
Cake can be turned over if desired onto serving platter. I just serve it from the pan the way it is.
Other fruit can be used prepared the same way .Blueberry Mash or Crushed Pineapple Mash or Rhubarb Mash you get the picture. Just adjust the jell-O flavor for each one!