Zelda Rubenstein
You may not recognize the name, but I bet you will recognize the face. Zelda Rubenstein passed away on January 27,2010 she was 76 years old. Zelda was born on May 28, 1933 in Pittsburgh, Pennsylvania. She stood only 4′3″ tall due to a deficiency in anterior pituitary gland which produces growth hormone. She lived in London for a few years and upon returning, at the age of 49, began her acting career.
She was cast as Tangina Barrons, the medium, in the movie Poltergeist. She also appeared in the two sequels and in a tv spin off. She appeared in Sixteen Candles, Cages, Teen Witch, The Wildcard, Southland Tales and National Lampoon’s Last Resorts. She also did voice over work and made numerous guest appearances.
Here is a clip from Poltergeist:

[...] famous author, wrote Catcher in the Rye Justin Mentell, appeared in Boston Legal, 27 years old Zelda Rubinstein, Poltergeist medium Pernell Roberts, Bonanza and Trapper John, MD James Mitchell, played Palmer [...]