Renard gets hold of the plutonium sphere from a bomb, forms it into a rod, and tries to insert it into the reactor of a submarine and cause a meltdown. Among the reasons this would never work: weapons-grade plutonium is less radioactive than reactor-grade plutonium. The reason you don't use reactor-grade Pu in a bomb is that the nuclear reaction will blow it to pieces part of the way through the detonation process, and you'll only get a small explosion.
Not to mention that Bond and Renard handle the plutonium bar with their bare hands. A rod of Pu that size would weigh at least 50 pounds, which is big enough to be a critical mass. It would be exceptionally hot to the touch, and also would be emitting lots of neutron radiation. Canadian physicist Louis Slotin was killed handling a much smaller critical mass of plutonium in a 1946 experimental accident; Slotin received a fatal dose in less than one second, and died of radiation sickness nine days later. The fact that Bond straddles the rod briefly may be a very subtle kind of Lampshade Hanging on why, in spite of his proclivities, James Bond never gets any Father's Day cards.
The reactor of the 1967-vintage nuclear sub had fuel assemblies (that plutonium rod) which could be manually inserted and removed. That's not how a Russian sub reactor is designed (though it is closer to certain heavy water power reactors.) To refuel the sub, they first need to shut down the reactor for 90 days so the fuel is not too hot from a radioactive and thermal standpoint. Then they cut open part of the sub's outside hull to remove the fuel assemblies. Big job, needed once every 5 to 10 years. The bullet stuck in the Renard's brain would have killed him by then and the audience would be quite bored.
Fake Brit: Elektra King, being half-British and half of Azeri descent, although her family had fled the Soviet Union many years earlier, manages to fit both this trope and Fake Russian at the same time, since she's played by Frenchwoman Sophie Marceau.
Fake Nationality: Renard, a Bosnian who worked for the KGB and then became a terrorist, is played by a Scot.
Fake Russian: Zukovsky, some others and half-way Elektra King- see above.
Star-Derailing Role: The much-maligned performance of Denise Richards pretty much derailed her rising career; her biggest role since this film was two years later as a middle-billed cast member in the slasher film Valentine.
Throw It In: The stunt of grabbing the cables on the Millenium Dome took several tries to get right. Apted put in one of the shots of the stuntman missing the cables to give a better sense of how hard it was.
You know how the Cold Open in this movie is the longest in the whole series? It was originally supposed to end after the bank scene in Spain, but test audiences thought that was too short. There had also been a plan for Elektra to survive and for Bond to visit her in the hospital where she was being treated for Stockholm Syndrome, but this was considered too downbeat.
Maria Grazia Cucinotta was considered for the role of Elektra, but this was nixed when it was discovered her English wasn't up to par. This did however, parlay into her brief but memorable role as the Cigar Girl Assassin.
Video game tie-ins for PlayStation 2 and PC were planned but cancelled. There were, however, versions on both the N64 and the PS1.