I read about Invader and his "invasion" a couple of years back. I thought it was really cool that there was someone scattering Space Invaders/Mario/Pacman themed tiles all over Paris! Here is a quick entry about Invader from Wikipedia:
"Invader (born 1969) is a French street artist who pastes up characters from and inspired by the Space Invaders game, made up of small coloured square tiles that form a mosaic. He does this in cities across the world, then documents this as an "Invasion", with maps of where to find each invader.He started this project in 1998 with the invasion of Paris - the city where he lives and the most invaded city to date - and then spread the invasion to 35 other cities in the world."
here to see the progress of the invasion around the world :)