The video above shows Tim McCready (from Auckland, New Zealand) visiting every London Underground station on the network. While this does not include the DLR or Overground, visiting all 270 tube stations is no easy feat. Plus, he's managed to choreograph himself, even though he filmed the stations out of order.
The only quibble tube purists might have about the video are the fact that he only includes one Hammersmith station (Circle and Hammersmith and City) and one Paddington station (Barkerloo, Circle and District) when there are in fact two of each. Still this is a very impressive achievement and one which I hope to match by walking between all the stations (overground). However, I still have a long way to go in my mission.
Found via this Reddit thread, where Tim explains how he went about filming himself at each station.