It's a good thing this public artist uses a pseudonym, because there's probably a whole pack of angry Parisians hunting for him after what he did to their commute.
"Farewell," as the urban hacker is calling himself, somehow obtained a uniform emblazoned with the logo for French public-transit operator RATP. With this, he was able to do a few devious things to a Metro car without attracting much attention. The first was to cover the inside with dark tape to give the windows the appearance of prison bars. The second alteration he pulled off with a socket tool that fit into the train's charmingly old-fashioned doors.
You can see what happened next below. Though entertaining, the video includes a bittersweet (and somewhat mysterious) in memoriam at the end. The artist writes:
My partner and I tried to carry out this intervention three years before. The result was unsatisfying and we promised ourselves to try again. The year after, my friend left us brutally. I hope he will like the result.
"Farewell" is something of an expert on wasting people's time. Here's another example, featuring police responding to a hollow person he built out of tape and set adrift on a river.