Haha, really?
Damn - I thought I was going to be original.
( Leningrad twitter.com/takebacks, Fri 25 Mar 2005, 20:56, archived)

I came up with it
When someone (I don't remember who) shopped Thomas the tank engine into a photo of the Potters bar thingy
( Brown cow, Fri 25 Mar 2005, 20:57, archived)