Dark side, or alternate reality, or something: NotStarring, the searchable database of actors who were almost cast in the movie roles you know and love. Like: David Bowie and Sean Connery in Lord of the Rings. Or: John Candy as Louis in Ghostbusters? And Eddie Murphy as Winston? Hours of totally useless movie trivia await you (yes, even more useless than your average movie trivia–if you can imagine that).
(Although, if it really matters to you, you should be warned that the database isn’t anything like 100% impervious to rumor and blatant untruths, as far as its verification scheme goes. But you knew that already, right?)