Fred Young did voice characterizations on this game. Our production run quantity of 500, which is sourced to the manufacturer via third party, is over twice the implied quantity on the Internet Pinball Serial Number Database (as of May 2021). Michael Gottlieb told us he has no memory of the production numbers for Alvin G, but when a quantity of less than half of 500 was once suggested to him as a better number for 'Mystery Castle', he felt it sounded right, saying "I know we did not build many."