Defines "Campy" One comment on the IMDB characterizes this movie as a "gay icon," and many others call it "campy." Since some people don't seem to understand this drift of thought, I'll try to give my two-cents worth of interpretation. There is a certain kind of gay male sensibility that loves the kind of over the top humor that predominates in "Baby Jane." I never thought of this movie as a horror movie, though it could fit the genre. But, really now, horror depends on a certain level of credible realism, as in "Psycho" and all of Hitchcock's films. That's why it is scary. Even modern horror films with monsters, UFOs, etc, rest on the premise that these are real phenomena and the movies ask us to suspend our disbelief within the context of the movie.
"Baby Jane" is completely different, and that is why it is campy and humorous. Elegantly serving your invalid sister a rat for dinner is just too much! Over the top. Unbelievable. Outrageous. Histrionic. Bette's makeup, ditto. Joan's completely loving and devoted manner, ditto. In other words, in spite of its literal horror aspects, "Baby Jane"--in its details--is too ridiculous to believe. Only a demented sicko (Bette's character) could possibly come up with these ideas, and only an equally demented and deluded sister (Jane's role) could find Bette in any way lovable or redeemable. Both roles are such exaggerations, such extremes, that they are funny, hilarious in fact. Even the sadistic treatment by Bette of longsuffering Joan is absurdly out of kilter. One can only laugh at the histrionics.
Of course, so much of the camp aspect of the movie depends on our previous knowledge of both these famous actresses. Especially important, is the long history of venomous lines uttered by Hollywood's most superbly bitchy star, Mme Davis. "All About Eve," of course, is the locus classicus for Bette's campy, dishy humor. It is another gay classic, one described elsewhere on the IMDB as "every drag queen's favorite movie."
"Baby Jane" is definitely a 10 out of 10.