Add Melissa Benoist to the list of ... um ... Well, gee (and Great Scott), how many actresses have played Supergirl?

IMDb lists 21 appearances of Supergirl as character (cf.: 248 appearances for Superman, 301 for Batman, 54 for Aquaman), but many are duplicates, or cartoons, or essentially fan fiction. So who really counts? 

Helen Slater appears on the list twice, for example: from the abysmal 1984 theatrical movie, and in a 2010 documentary called “Heroic Ambition,” all about Metropolis, Ill., and its annual Superman celebration. The second actress to play Supergirl was Nicholle Tom, who voiced the Girl of Steel in five episodes of “Superman: The Animated Series,” one episode of “Batman: The New Adventures,” and seven episodes of “Justice League.” Other cartoon Supergirls include Nicole Sullivan (of “Mad TV” fame) in the short-lived “Super Best Friends Forever,” Summer Glau in “Superman/Batman: Apocalypse,” and Molly Quinn in “Superman: Unbound.”

For live-action Supergirls after Slater? There's Laura Vandervoort, who had a recurring role as Kara/Supergirl on “Smallville”; but IMDb also counts Michelle Prenez, who did a comic turn as the Girl of Steel on “Jimmy Kimmel Live!,” Lissy Smith in Max Landis' straight-to-YouTube hit “The Death and Return of Superman,” Kristen Bell as “Fake Supergirl” in “Movie 43,” and various forms of fan fiction (Briana Stancer; Jaclyn DeDoux). 

If you eliminate the fan fiction, short comic turns, and dupes, you wind up with only six previous Supergirls: Slater, Vandervoort, Tom, Sullivan, Glau and Quinn. 

If you eliminate the cartoons, you wind up with only two previous Supergirls: Slater and Vandervoort. 

But if you only count actresses who have played Supergirl in movies or TV shows about Supergirl? Then it only happened once before. And that one sucked. 

SLIDESHOW: A HISTORY OF SUPERGIRL ON SCREEN