Clay animation is a form of stop motion animation, were each animated piece, either character or background, is "deformable"—made of a malleable substance, usually Plasticine clay.
Some well known claymation are:
Wallace and Gromit (1989)
Purple and Brown (2006 - 2007)
James and the giant Peach (1996)
Clay-animated films were produced in the United States as early as 1908, when Edison Manufacturing released a trick film entitled The Sculptor's Welsh Rarebit Dream. In 1916, clay animation became something of a fad, as an artist from the east coast by the name of Helena Smith Dayton and a West Coast animator named Willie Hopkins produced claymation films on a wide range of subjects. Hopkins in particular was quite prolific, producing over fifty clay-animated segments for the weekly Universal Screen Magazine. Increasingly, three-dimensional forms such as clay were driven into relative obscurity as the cel method became the preferred method for the studio cartoon around the 1920's.