The game was devised by three college students, Mike Ginelli, Craig Fass, and Brian Turtle in 1994. Its name is a pun on the stage play Six Degrees of Separation, based on the title rhyming with Kevin Bacon's name.

The concept is simple, but finding the smallest number of links can be difficult. The way you link an actor with Bacon is like so:

    * Pick any film actor in history.
    * Link the actor you've chosen to Bacon via the movies they've shared with other actors until you end up with Kevin Bacon himself.

Here is an example, using Elvis Presley:

   1. Elvis Presley was in Change of Habit (1969) with Edward Asner
   2. Edward Asner was in JFK (1991) with Kevin Bacon

Therefore Elvis Presley has a Bacon number of 2.

The game has expanded to become more about linking two film actors than just one actor to Kevin Bacon. The name is still retained, however, because it has been shown that Bacon is a common link member in a chain.

Notably, Bacon is not the most linkable actor. According to the Oracle of Bacon site, that honour goes to Rod Steiger. The average Steiger number in the acting community is 2.679.[1] By contrast, the average Bacon number is 2.946.[2]

Very few actors have an undefined (or infinite) Bacon number, meaning that they cannot be linked to Bacon in any number of connections at all. For instance, Fred Ott appears in the 1894 Edison Kinetoscopic Record of a Sneeze; he was the only actor in that film and also acted solo in Fred Ott Holding a Bird — the only films in which he appeared. (It should be noted that Ott was not a professional actor; he was a lab technician in the laboratory where Edison's Kinetoscope was developed.) Most actors, however, can be linked to Bacon. As of December 2005, there were 9,692 actors in the IMDb who could not be linked to Kevin Bacon out of the total of 418,468 (approx. 2.3%).[3]

The Six Degrees of Kevin Bacon game sometimes fails to model the real world as it allows both forward and backward linkings. Very frequently, only one kind of linking is allowed between two nodes.

For example, the spreading of any virus is forward in time. If John Doe catches a virus on Monday, Jane Doe, who only had contact with him two days before that could not get the virus because of her previous contact with John. However if she came into contact with him after she may contract the virus.

For John Doe to transmit the virus to Jane Doe, it may require following steps:

    John Doe -> Jack (3 days later) -> Tom (3 days later) -> Jane Doe (3 days later)

However, if John Doe is running a peer-to-peer file exchange program like Kazaa, he needs links backward in time. He does not care who will get a piece of the file in the future. He wants to know who already had that piece of file at hand.

For John Doe to receive a piece of file, that particular information could be travelling in this manner: