(written from a Production point of view)
Antoinette Bower (born 30 September 1932; age 84) is the German-born actress who played Sylvia in the Star Trek episode "Catspaw". She filmed her scenes between Friday 5 May 1967 and Wednesday 10 May 1967 at Desilu Stage 8.
She has many other television guest roles to her credit – between 1959 to the 1980s, she amassed almost ninety appearances on such programs as Perry Mason, The Twilight Zone, Ben Casey, The Fugitive, Mission: Impossible, and Murder, She Wrote. She has also starred in many made-for-television movies, including 1974's movie Columbo: Negative Reaction, in which she co-starred also with fellow TOS guest performers Michael Strong and Bill Zuckert, and 1984's The Cowboy and the Ballerina, with Christopher Lloyd and Michael Pataki.
In 1983, she co-starred with Philip Anglim, John de Lancie, Richard Kiley, Christopher Plummer, Jean Simmons, and Meg Wyllie in the epic TV mini-series The Thorn Birds. And from 1990 through 1992, she was a regular on the TV series Neon Rider.
She also built a portfolio of supporting roles in feature films, making her debut with an uncredited role in the 1962 classic Mutiny on the Bounty. She followed this with yet another uncredited appearance in the 1971 horror movie The Mephisto Waltz, starring TOS guest actor William Windom. She later had a supporting role in the popular 1980 horror film Prom Night, directed by Paul Lynch. Her other films include The Evil That Men Do (1984, with John Glover) and Club Paradise (1986, with Joanna Cassidy, Andrea Martin, and Bruce McGill).
Star Trek Production Assistant Charles Washburn, in an interview, declared her the most professional actress with whom he had worked on the series.