The film was originally going to be a "Jump Street" - "Men in Black" crossover with Channing Tatum and Jonah Hill reprising their roles. However, plans fell apart, so it became a spin-off, with Chris Hemsworth and Tessa Thompson.
This is F. Gary Gray's second film, since his directorial debut Friday (1995), to be shot in the taller 1.85:1 aspect ratio, although presented theatrically in the Univisium 2.00:1 aspect ratio. It is also the first Men In Black movie to be presented in the Univisium aspect ratio.
This is the first Men in Black film to be given a BBFC (British Board of Film Classification) '12A' rating in the U.K. (the U.K. equivalent of the MPAA's 'PG-13' in the U.S.A.). The previous films were all rated 'PG' in Great Britain.
Frank the Pug (voiced by Tim Blaney) and the Worm Guys (voiced by Thom Fountain) are the only characters from the first film to also physically appear in this one. Although they have a prominent place on the movie's poster, these characters have less than a minute of screen-time.
Agent J, Agent K and Frank the Pug are the only characters to appear in some form in every Men in Black movie. Agents J and K were characters in the first three movies, and appear in a painting in this one; Frank was in the first, second and fourth movie, and appeared on a picture in J's living room in the third.
The trivia item below may give away important plot points.
Tommy Lee Jones and Will Smith stated that they would not return for this film. They do appear briefly, in a painting in the London MiB office, which is a dramatized depiction of their fight with the Edgar-bug from Men in Black (1997).