Oh, what a nice, inviting chair! I think I'll sit dowOH MY GOD WHAT IS THAT WHY?

Designboom describe's Yaara Derkel's "Coppelius Chair":

...is an object simplistic and lifeless, or does it eclipse another living entity? this doubt, which sometimes arises within us and destabilizes our basic feeling of safety, was called by freud 'the uncanny'. it refers to when something usually recognized as familiar and comfortable radiates foreignism and even hostility...

...the psychological concept assumes the shape of a wooden chair – a well known and likeable [sic] piece of furniture which gives off homeliness and a warm, welcoming ambience. 'it so common and familiar, that it's hard to imagine as having any sort of duality. the presence of the sitter is also found in his absence- the folds of the cloth, the fissure of the pillow, the scratched timber,' explains derkel. thus, the challenge was to create two characters simultaneously. on one hand, the familiar typology, and on the other, 'the stranger', a hidden, unknown identity, impossible to observe at first sight.

More info at Designboom. Complement with more cases of pareidolia.

H/t Wil Wheaton