He mentioned it on his forums once, way back in 2007 when I was preparing to be on the show myself:
http://www.ken-jennings.com/messageboards/viewtopic.php?p=12...
(Tuesday Trivia is his weekly email trivia contest.)
http://www.ken-jennings.com/messageboards/viewtopic.php?p=12...
(Tuesday Trivia is his weekly email trivia contest.)
I ended up 72 victories short of Ken, though.