Bake the cupcakes according to the directions on your box or recipe. Line the cupcake tins with cute liners. It always matters. Once they’re baked, let them cool completely.
Once the cupcakes are cool, grab the piping bag and swirl a generous, smooth frosting layer over each one. Pro Tip: If you don't have a piping bag or tip, a plastic zip-top bag with the corner snipped off works. Starting on one side of the cupcake, start pressing your M&M’s into the frosting. Lay them down overlapping slightly, kind of like fish scales. Just make sure to leave an oval-shaped blank space on the opposite side of the cupcake that’s where the fish’s face will go.
Pop a sugar eye right onto the blank space you left. You can also use a white chocolate chip with a tiny dot of black icing works too. Even a small candy like a white M&M could do in a pinch.
Grab a piece of rainbow candy strip and cut it into a triangle shape. Stick it into the back of your fish (the side opposite the face), with the wide part sticking out to look like a tail fin.