Dutch artist M.C. Escher named one his curiouser creatures De Pedalternorotandomovens centroeulatus articulosus, to which he thankfully gave the common names of wentelteefje (for females) and rolpens (for males).

These are both references to oddly-named Dutch foods, perhaps with the idea that they sound like animals more than food, so let's just fix that. Wentelteefje, as noted above, is what Americans call French toast and the Dutch call a "little flipbitch" (wentelen, rotating; teef, female dog; -je, young; this is probably a folk etymology), while rolpens is 'rolltripe', a portmanteau of rollmops (pickled herring) and pens (tripe) used to refer to a rather interesting sort of traditional sausage.

These creatures were invented, by Escher's own report, due to the disturbing lack of wheel-shaped creatures in nature. He constructed them first out of clay, and then copied them into ink. They have segmented bodies not dissimilar to a centipede, but with six humanoid legs. They have a chunky head with a beaked nose and flat black eyes protruding to the sides on short stumpy stalks. When they roll up the eyes become the axis, and the long tail wraps around to make a solid wheel; the legs can be used to push the creature along, or can be folded up to the body. Despite the difference in naming, there is no obvious sexual dimorphism among these creatures.

In English we usually translate both wentelteefje and rolpens with the single, boring, unimaginative name of curl-up. These creatures are best known from Escher's lithographs Curl-up (or Wentelteefje, in the original Dutch), in which a series of the creatures are curling up and rolling across a block of text, and House of Stairs, in which they climb a complex series of impossible staircases.

Wentelteefje is pronounced something like 'ventelteyfyeh' (IPA /ˈʋɛn.təlˌteːf.jə/). If you are having trouble visualizing one, they are well worth a quick internet search.