Sidewalk chalk illusion
The way they put the chalk on the sidewalk it makes it look like a snowman.
The thing that makes this chalk stand out are the shadows that make it stand out and the perspective of the person that is seeing it at. If you look at it from the wrong angle all you can see is chalk in blobs. You have to be there right when it's finished because it Only lasts until it rains or fades away.
"Secrets Behind the Sidewalk: How 3D Sidewalk Art Is Made." Creative Guerrilla Marketing. N.p., 20 May 2014. Web. 18 Mar. 2015.
"Swimming Pool Chalk Drawing Optical Illusion." Mighty Optical Illusions RSS. N.p., 10 Dec. 2014. Web. 18 Mar. 2015.