Bioloids are biosynthetic machines typically designed to mimick another being. However, bioloids often lack memories or personality traits that the real person would have.

On Farscape, the Scarrans have mastered the technology and have used it to replace multiple members of the Moya crew. At their secret base on Katratzi, they have a contraption called a bioloid duplicator, presumably used to create bioloids.

In the episode "Bringing Home the Beacon," Aeryn Sun was captured by the Scarrans and replaced with a bioloid. It isn't until John Crichton mentions her pregnancy, and Aeryn doesn't know what he's talking about, that Crichton realizes something is amiss. He shoots her face, which reveals the biomachinery that lay underneath her skin.

Later, the Scarran emperor Staleek replaces Stark with a bioloid that seemingly tortures Scorpius. However, this is all a ruse in order to hide the fact from Ahkna that Scorpius is working for Staleek. Scorpius quickly realizes Stark has been replaced since the real Stark would never torture anybody, even fictitiously.

Sikozu is also a bioloid, albeit a different type, as revealed in conversation with Zukash in "Hot to Katratzi" ("How many other bioloids are here?"). Both Kalish signal to each other they're bioloids by rotating their eyes around to reveal a star-like pattern on the back. Sikozu is specifically designed to be a weapon against the Scarrans by emitting intense radiation that destroys their heat-producing gland.