Não significa nada. Foi uma escolha aleatória.
The title of the film, Movie 43—first believed to be referencing the number of actors in the film—actually has no meaning. Farrelly heard his son talking with friends about a film called "Movie 43", but when Farrelly discovered the film did not actually exist, he cribbed the name
Eu também encontrei isso
Q: What exactly does the title, Movie 43, mean? A: According to Wikipedia, the title references one of the sketches in the film where a bunch of teenagers are surfing on the internet looking for a banned movie called Movie 43. Apparently this has to do with the 43rd rule of the Internet, which is that if you search long enough you will find something.
Estou procurando e encontrei regras de internet, mas 43 não é "pesquisar tempo suficiente e você encontrará algo", em vez disso parece ser "Quanto mais bonito e puro é, mais satisfatório é corrompê-lo. "