Sim was a mimetic simbiot of Commander Charles Tucker III, created by Doctor Phlox using a Lyssarian Desert Larvae. He was created after Tucker was injured and rendered comatose due to an encounter with a spatial anomaly in 2153. Sim's purpose was to provide Phlox with vital brain tissue, which was used to treat Tucker's condition. Sim resided aboard Enterprise NX-01, where he lived a lifetime in fifteen days.
