However, the inventiveness of the Stickers on the Central Line series which first started appearing last year took things to a new level with an accompanying blog and commentary
I love the explanation for Lille: "It is a little known fact that
between Woodford and Buckhurst Hill there is a lightly used tunnel which
provides London Underground commuters direct access to the Paris Metro.
Providing you’re not in a hurry, you can just sit back (if you can find
a seat), relax and simply show your passport when the border guards
pass through the train."
The stickers have also made their way onto other trains in London such as the Gatwick Express
As Andy points out in his article there are some websites around that are selling the stickers, and now that the "craze" has been published in The Sun today & on Mashable in the US, one can only imagine there will be even more interest and even more inventiveness in the creations.
If you spot any more on your journeys, let me know.