The House of Humor and Satire, Gabrovo, Bulgaria
The Gabrovonian cat, with cropped tail so it doesn't need as much time to go in and out of the house (which would increase the heating bill).
Hypercube - a cube made of semi-transparent glass that is finite on the outside and infinite on the inside.
The Gabergé Egg - a little tap is fixed to the egg so it lasts longer.