Creatures on the walls

For a while now i was spotting these in the streets of Amsterdam. They kinda make me think of friendly aliens coming to visit us. hihi.
Then like last week there was an item on a children's network about graffiti and spraying the walls. In the night they went out with two graffiti artists. At one point during the interview it was asked what they were going to do next. "Make some little creatures" the guy with the spraycan said, turned around and started making (my) friendly aliens! Ha.