A mimetic simbiot is a clone created by a Lyssarrian desert larvae that has been injected with DNA from another organism. Simbiots are identical to the original genetic donor, except that they undergo their entire life cycle in only fifteen days. The Lyssarrian Prime Conclave bans the creation of simbiots, due to the ethical ramifications of creating living, sentient beings. This dictate was defied by the Velandran Circle, a group of Lyssarrian scientists, whose illegal research on simbiots have also led them to make largely unsubstantiated claims of a way to stop the rapid aging process.

In 2153, Doctor Phlox created a mimetic simbiot (named "Sim") of Charles Tucker III to serve as a tissue donor, after the real Tucker was injured in an engineering accident. (ENT: "Similitude")