Get your pony. It doesn't really have to be a My Little Pony figure, it can be any kind of pony you want.
(optional) If you don't like the color of your pony's hair, it can be changed. I used some left over hair dye on mine. KoolAid works just as well.
Take your acrylic black paint and brush. (I used a sponge brush.) Coat your pony once and let dry. When its dry, paint another coat of black on.
For the batman symbol, I did it free hand, but an easier way would be to print or draw a small symbol on paper, cut it out and hold it in place on the pony while you paint yellow around it. (I don't recommend taping it to your pony, the black paint will come off.)