Erin Margaret Murphy
(born June 17, 1964, Encino, California) is an American actress who is best known for her role as young Tabitha Stephens on the top-ten television sitcom Bewitched, which ran from 19641972. For the first season she shared this role with her sister, Diane, as they were of similar appearance and stature. As they got older and looked less alike, Erin played the part alone.
http://en.wikipedia.org/wiki/Erin_Murphy

http://www.imdb.com/name/nm0614249/