Real World article(written from a Production point of view)
Thelma Tyrell is an actress who was a regular background performer on the first season of Star Trek: Enterprise. She portrayed a Starfleet engineer but received no credit for her appearances.
According to Ms. Tyrell, she wore a wig on her appearances on Enterprise. Her appearance in the episode "Fallen Hero" was cut out from the episode but was later included in the ENT Season 1 DVD.