I thought of a game, but I don't have a catchy name for it. It's like six degrees of separation, but you take someone you already know directly, and find a secondary route linking you and that person. The rule is that there has to be at least one person in the chain that neither of the two people at the end knows.

For example: Bob is a former co-worker. So I know Bob directly. So to find a secondary chain:

1. Bob used to go to high school with George.
2. George is friends with Mike.
3. Mike used to be in a band with Dan.
4. Dan used to go to high school with me.

Bob doesn't know Mike or Dan, and I don't know George or Mike, so this route is valid.

You have to take the shortest possible secondary route, so no inserting extra people just to have someone you don't know in there. For instance, in the example above, if I knew George directly, Mike and Dan would have to be removed, and this route wouldn't be valid because the two ends (me and Bob) would know everyone in the middle (George).