Over at Slate, Ben Blatt has put together something amazing and useless and entirely engrossing. Plug in any two athletes from the history of professional baseball, football, and basketball, and it will connect them via teammates in as few steps as possible.
(Update: Slate's tool is having issues thanks to heavy traffic. If it's not working for you, head back later and try again.)
Tapping the databases of the Sports-Reference.com sites, Blatt's widget contains 4,000 basketball players dating back to the BAA of the 1940s, 23,000 football players going back to the 20's, and 18,000 baseball players stretching all the way back to the 1870s.
The fun is in trying to beat the system. Pick two of the most obscure athletes you can think of, even from two different sports and separated by more than a century, and the tool will link them. No two athletes are separated by more than 12 steps, and the vast majority can be done in nine or fewer.
The secret is the multi-sport athletes. You'll see names like Deion Sanders, Bo Jackson, Drew Henson, and Mark Hendrickson pop up a lot to bridge the gap between the NFL and MLB, or MLB and the NBA.
(This is why hockey players miss out on the fun. Blatt's tool does contain NHL players, and can link any two, but since no professional hockey player has ever played at the top level in another sport, the chain can't jump to other sports.)
So go mess around with "Six Degrees of Kevin Garnett" for a few minutes, or the rest of the day. Report back with any fun connections, or the holy grail: a 12-step chain.