So I made the normal Rice Krispie Treat recipe and put it all in a spring form pan. I patted it down quickly, and before it cooled, I placed a plate upside down on the top of the cake, flipped it over on the plate, held it over the sink and dropped sprinkles on the sides.
Be careful - since the "cake" is still warm, it can easily break apart.
To find the recipe, Google "original Rice Krispie Treat recipe".
Now for Jill's birthday present (her choice):