Planet
The smallest known planet is PSR B1257+12A, one of the first extrasolar planets discovered, which was found in 1992 in orbit around a pulsar. Its mass is roughly half that of the planet Mercury. The smallest known planet orbiting a main-sequence star other than the Sun is Kepler-37b, with a mass (and radius) slightly higher than that of the Moon.
Least pygmy squirrel
The least pygmy squirrel ("Exilisciurus exilis"), also known as the plain pygmy squirrel, is a species of rodent in the family Sciuridae. This plain olive-brown squirrel is endemic to forest in Borneo and the Banggi Island. It is among the smallest squirrels in the world.