CompatibilityAlley Cat was one of the few games of the 1980s that was programmed with full attention to different PC speeds. It's an early, old game--yet it runs perfectly on any machine. The reason it runs on any computer today is, upon loading, the first thing it performs is a mathematical routine to determine the speed of your processor, and as of 2003 we've yet to build an Intel PC too fast to play it.
PCjr / Tandy supportThe game supports the PCjr out of the box and uses an alternate CGA palette. However, Tandy support wasn't available until an amateur patch was created in 2015. It can be found here.
Hidden messageBill Williams hid the message, "MAY GOD BLESS YOU AND KEEP YOU" within the programming code of the game.
SalesBill Williams only made $600 on Alley Cat.
Information also contributed by: WizardX