Men in Black III is a good film, not a great one. I think it is a step up from Men in Black II. It was fun to see the characters again and the makeup and effects for the various aliens were good. Maybe no sequel can ever recapture the fun of the first film in the series.
In this one agent J goes back in time to save the life of agent K. An alien criminal, Boris the Animal, has broken free from a supermax prison on the moon and has gone back to 1969 to kill a young agent K. This will allow his race to conquer or destroy Earth. Boris the Animal is not that interesting to be honest and even having two of him on-screen at the same time does not make him more interesting. (The present verion of Boris talking to the past verison of himself is not nearly as much fun as it was when the two Spocks talked in Star Trek.)
An Entertainment Weekly review said that the plot of the movie’s last 15 minutes makes no sense. It is worth seeing.
The movie has some nice moments and Josh Brolin is really good as the young agent K. (This beats having Tommy Lee Jones in bad makeup trying to pass as a much younger agent K.) This limits Tommy Lee Jones to essentially a small role in the movie. It worked I guess but that does suggest that Jones is bored with the franchise to an extent. Perhaps he is not bored with the series.
Rip Torn is missed as the head of MIB, Zed. His character died during the film. Torn brought something to the series. Emma Thompson plays agent O, who takes over as the head of MIB.
David Rasche, always to be remembered as Sledge Hammer, appears briefly in the film. His appearance is all too brief. It seems a waste to have him and not do more with him.