Ink and pencil
Go-a-Green-a
Endless staircase with characters from Futurama animation series. See also frames with Escher inspired scenes from Futurama.
Artist's deviantART profile http://go-a-green-a.deviantart.com.
The image was found at http://go-a-green-a.deviantart.com/art/Penrose-245904421.