William Prall is a baseball player Aldo and Lincoln went to watch when Lincoln was younger and Aldo said he was his favorite player and he used this name when Lincoln saw him in the viewing room when he was in the electric chair.
There was a real pitcher for the Chicago Cubs named Willie Prall, although his full first name was Wilfred and not William. He played for one year, 1975, going 0-2 with an 8.59 ERA. He wore #37, as opposed to the #11 on the show. Prall also threw left-handed in real life as opposed to right-handed in the show.