Curly dressed as a woman 13 times. Here is a list of films that featured him in drag:
Three Little Pigskins
Pop Goes the Easel
Uncivil Warriors
Movie Maniacs
Whoops, I'm an Indian!
Wee Wee Monsieur
Mutts to You
Oily to Bed, Oily to Rise
Nutty but Nice
Matri-Phony
Micro-Phonies
Uncivil Warbirds
Rhythm and Weep
For the record, Larry was in drag 13 times, Moe appeared in drag 10 times, Shemp was in drag 3 times, Curly-Joe was in drag once. Joe Besser was the only Stooge to never dress like a woman in a Stooge film. Final total of Stooge drag appearances: 40