The first alien in the mail room that Will Smith starts to talk to in alien language is a rapper known in real life as Biz Markie. He is really making those noises with his mouth.

In David Cross' room, next to the TV in the pile of videos, is a copy of the original Men in Black movie from 1997.

In the MIB head quarters, when they've got the inspecting thing you go past (this is almost right before Serleena takes over the building), you can see a bald looking alien. You then watch from the back view as a ponytailed, earring wearing man puts a wig on the alien to make it look human. The man with the ponytail is Academy Award Winner Rick Baker, who did all the makeup effects for this film and the first Men In Black film.

Towards the end when J and K are flying in the jetcar (or whatever) to get away from Serleena, they neuralyze two kids in the street. The two kids are Will Smith's sons.

When J & K go to K's old house and there is a family sat on the sofa, centre of the three people is the movie's director Barry Sonnenfeld. The little girl on the couch of K's old house is Tommy Lee Jones's daughter, Victoria. The mom is played by associate producer Stephanie Kemp. Sonnefeld was horrified to see he had a bald patch and wanted it covered by CGI. (From the DVD Audio Comentary with Barry Sonnefeld.)

The little girl who asks Kay for stamps in the post office and Jay lifts out of the way is the director (Barry Sonnefeld)'s daughter.

At Grand Central station they go to locker C-18, which contains the little fuzzy creatures. The director stole his own sequence from "Get Shorty" (at the airport with John Travolta) including the same locker number (from the DVD Audio Commentary with Barry Sonnefeld).

In the pizza parlour, the guy wearing the astronaut suit in the picture is production designer Bo Welch.

In the room where J fights Jarra, there are a lot of ships and equipment laying around. In the shots where J is talking to Jarra there is a ship located behind J and to the left. Although it's been given a shiny chrome look for the movie, this is the same ship that was used in the 1963 TV series "My Favorite Martian," that starred Ray Walston and Bill Bixby.

The beat box sound that Will Smith does in the backroom of the post office is the same one he did on The Fresh Prince of Bel Air to Ashley.

There are two different versions of the scene where Jay and Kevin/Kay first enter the deneuralyzer: one with Kevin in his civilian post-office uniform (seen in the trailer) and one with Kevin in his old MIB suit (seen in the film).

In the sceen when J is in the mail room with K and the three aliens are revealing themselves the one that removes half of his his body in the middle is John Andrew Berton Jr., who is the visual effects supervisor for Men in Black II.

When J neuralizes the other agent in the cafe he tells one of the waitresses that he likes her. This waitress is Barry Sonnefeld's step-daughter.