Add a single banana or a bunch to the top of your cupcake. Could the banana decoration be a clue that the cupcake is banana flavored?
Using Tip 8 with yellow buttercream icing, pipe crescent shape . Start squeezing with even pressure and increase slightly for the center area, then back to even pressure for the other end.
Pipe Tip 3 stem and bottom accent with brown buttercream icing. For a bunch of bananas, pipe the bottom ones first, then overlap the next row slightly as you move upward to form a bunch.