The initial installment benefited from being fresh, unusual, and amusing—a playful send-up of science fiction tropes featuring two memorable detectives attempting to avert global catastrophe. This sequel struggles to maintain that appeal, forcing the enjoyable concept into a follow-up that falls short in terms of quality writing and substance. Even Tommy Lee Jones ("K") and Will Smith ("J") are given insufficient material to elevate the film beyond a forgettable narrative dominated by a talking dog. The plot centers on "K" having departed from the "MIB," naturally erasing his experiences within the organization. As another potential worldwide disaster arises, “J” understands that reactivating his former mentor's memories is their only chance—and needs to happen fast. This proves more difficult than imagined. However, "J" begins to understand that "K" had foreseen a possible need for his return and left behind some memory triggers for them both to discover, hopefully restoring him to operational readiness. The story’s focus has shifted, placing the frequently bothersome “J” in a position of prominence far too often, and "Z" (Rip Torn) doesn't leave much of an impression either, as we are presented with a showcase of alien designs reliant on special effects that manage to inject some amusement into this otherwise unsatisfactory continuation. There’s excessive talking and an overabundance of Will Smith—one film was sufficient.

Source on TMDB