Toast both of the cinnamon toast waffles. When they're ready, cut the little toast pieces apart.
Spread marshmallow fluff on half of the toast pieces, and spread peanut butter on the other half. (Notice how my toast pieces were disappearing? Grace was sitting at the table, stealing them when I wasn't looking. She had eaten her snack before I assembled and photographed the sandwiches.)
Place one slice of banana on top of the fluff on half of the toasts.
Stick the peanut butter on top of the fluff and banana. Serve while the toast is still warm from the toaster.