have the 2 old guys (hecklers) in the top left or top right corner heckling you

Have to be pop up trolls that you could bash in the style of MM, swinks, (with a punchline each time you belted one with the ball).

Knowing Stern though they would just use printed decals rather than actual rubber castings of them. ;)

Statler and Waldorf, I just googled it.