We saw our share of demonstrations, street art, and public theater in Paris. But only once did I see politically-motivated Aquascript (TM).
On the occasion of la Journée Mondiale de l'Eau (World Water Day), April 12, 2010, basic-needs NGO Solidarité International sponsored an art installation that used carefully timed droplets of water to depict bombs and form words saying things like, "I am the leading cause of death, more than . . ." and the same thing in French. I didn't get shots of all the words, but I did get a few of the bombs and a skull-and-crossbones. Sorry it's all backwards - I caught this while still mounted on a Vélib' on my way to the library.
Pretty nifty, eh? You can see a video if the set-up and full execution of the installation at Aquascript's website (see above).
The Place du Palais Royal's placement across from an entrance to the Louvre makes it one of the most central, most visible public spaces in the city. As such, there are new demonstrations, art installations, and events almost every week. It's a spot that's worth passing by often, and once you're there, plan on making like this Aquascript installation - just go with the flow.