What is Mornington Crescent?

Mornington Crescent is a game which involves mentioning (train/tube/whatever) stations connected to other stations. The idea of the game, is to keep playing.

When someone reaches Mornington Crescent, the game ends.

For further information, see
the Wikipedia Mornington Crescent entry or this page http://www.mornington-crescent-rule.fsnet.co.uk/mornington-crescent-rules.htm.

You can also play Mornington Crescent online

But seriously...

There are both no rules, and infinite rules. If you name a rule, you can probably use it. Watch a game, and once you realise it makes no sense, it makes perfect sense.