The title is in reference to the forgetful tendencies of the heroine, Lucy. The irony is apparent—a first time is supposed to happen just once, thus the meaning... is basically not literal. Without seeing the film, one would have difficulty trying to figure out what the movie entails, and this is but a typical character of most American makes. The number 50 could have just been selected at random, since any number, save for 1, would deliver the message the writer intends to convey.
50 First Dates featured quite a lot of humorous circumstances, from the unusual personality of the supporting characters to the on and off romance between the two lead roles....