Pythomnia

Pythomnia is an incredibly dense planet about the size of a large asteroid. Its core is composed of part of a neutron star, giving it a gravity comparable to a small gas giant. However, its atmosphere is very thin and in fact habitable, home to a species of intelligent Pythomnians. They are usually 0.5 mm tall (about the size of the Earth tardigrade), though when they spend extended times outside Pythomnia's gravitational field, they tend to grow larger without limit, with recorded sizes up to 2 mm. Pythomnians are almost as intelligent as humans (they never developed calculus) and maintain a civilization of about 2 million individuals. Pythomnians are technically single-cell organisms, but they are very complex, with fairly developed eyes and speech, and are capable of changing their color and shape at will. A notable member of this species is Invisiblob.