Paris is literally invaded by them little creatures, and this is no coincidence: Invader, the artist who brought them from an old console/computer game into real life since 1998, is said to live in this town.
They are always sitting in places you would not expect them to, always making you discover interesting corners or weird architectural details or interesting situations.
Some people do visit towns by following his little characters made of mosaic tiles. There are even online maps to check out where they are, but beware, some might be gone by the time you arrive there ...
Invader's Website
Interactive map of geotagged space invaders.