- The plot contains several direct echoes of Toho's classic mid-70s double-feature "Godzilla vs. Mechagodzilla" and "Terror of Mechagodzilla." which was released in 1975. Godzilla is initially perceived as a destructive force in each film, but he is eventually revealed to be a relatively innocent victim of mistaken identity. In addition, during the monster fights in each film, Godzilla and Mechagodzilla both fire their atomic breaths directly at each other at exactly the same time, resulting in a battle for dominance between the two atomic blasts, with Mechagodzilla's winning each and every time. Also, in each film, including the current one, Mechagodzilla is vanquished by a beheading. In the Toho films, Godzilla is the one who rips the head off of his metallic adversary's body. But in this film it's Kong who rips its head off.
- King Kong is seen eating a squid in his first film (while also indirectly devouring a human soldier), and sucking out the brain of a Warbat (huge flying serpent) in Godzilla vs. King Kong. Kong is also shown eating a squid in Godzilla vs. Kong: King of the Monsters. Real gorillas are nearly entirely herbivores; they may sometimes consume termites to help in the relief of diarrhea, but that's about all they eat. It has been subverted since, although though King Kong is described as a "epic" ape, he does not resemble the 2005 film's "epic" gorilla (for example, he is largely bipedal and lacks the pot-belly gorillas have for digesting tough plant stuff).
- Fans may have missed a little feature in Mechagodzilla's design, according to VFX supervisor Bryan Hirota, who disclosed it in the following way: In the film, "a lot of this stuff isn't that visible, but if you were to close-up on any of these joints, there are mechanical armatures that move pieces out of the way so that he can close his elbow joints or close his knee joints," Hirota explained to Screen Rant. "A lot of this stuff isn't that visible in the film, but if you were to close-up on any of these joints, there are mechanical armatures that move pieces out of the way "While staying within the authorized design, we altered the feet to provide more utility at the locations when it was necessary to shift the feet. Some of his armaments were already evident on him, such as the rocket packs that hung over his shoulders and the machine guns "In his words, "he went on." In developing the action scene, with Mecha eventually facing both Godzilla and King Kong, we were just searching for extra weaponry to bring into the battle, since historically, Mechagodzilla is loaded to the teeth," says director Gareth Edwards.
- The Hellhawks were referred to as Yoshuma throughout manufacture. On the package of a Playmates mini-figure, their eventual name was revealed.
- The fact that Ghidorah's skull still contains remnants of the three-headed destroyer's consciousness, which allows the Mecha to be imbued with Ghidorah's sadistic personality, means that it is in many ways Ghidorah's successor.
- A prevalent belief is that MechaGodzilla was involved, either framing Godzilla for the assaults or misinterpreting Godzilla's quest for MechaGodzilla as unprovoked aggression, however neither theory has been proven. That's exactly what happened. It was widely thought that King Ghidorah's bones inspired MechaGodzilla. MechaGodzilla's operating system is Ghidorah's brain and telepathic communication. A few speculated that Kong was really battling MechaGodzilla disguised as Godzilla. In order to avoid being misled by the title, some assumed that actual Godzilla and Kong would battle in the movie. A few people took the "One Will Fall" tagline literally, doubting that either Godzilla or Kong would die in the film. Both Titans survive the film and agree not to cross paths.
- Playmates Warbats, Hellhawks, and MECHAGODZILLA were unveiled in early peeks and leaked photographs much before the official trailer. Kong and Godzilla are both shown with terrible wounds, including a diagonal deep slash across King Kong's whole body. Pop! released a Mechagodzilla Pop!, essentially destroying the character.
- The events of Godzilla: King of the Monsters take place five years after the events of Kong: Skull Island, which took place in 1973, and fifty years after the events of Godzilla: King of the Monsters.
- For example, their connection contains some of these characteristics: Even though Jia communicates with Kong mostly via sign language, Kong feels and thinks as if he can read Jia's thoughts and feelings at all times. Whether it's because she knows him so well or because of a mystical/telepathic link that was hinted at in the titles of the last film, it's unknown. To make matters worse, in the novelization, Kong only notices Jia's plight after the latter had said a quiet Iwi prayer in his direction. It's not clear whether he showed there because of a fluke or if her prayer had any other effect.
- The moaning sound MechaGodzilla makes after Kong decapitates it is a reference to the Femuto's death in Godzilla (2014) and the sound Rodan makes after being stabbed by Mothra in Godzilla (1980).
- When asked about a possible crossover between Pacific Rim and the Monsterverse, Steven S. Denite, the director of Pacific Rim Uprising (2018), said that talks are in the works. He said in an interview with Bloody Disgusting: "There's been a lot of talk about crossing over. Look, I think it would be great if the Pacific Rim universe joined Legendary's Monster Universe; it seems like a natural progression." He even admitted that as a fan, he would be excited to see it.
- According to writer Max Borenstein, the screenplay he developed for the film Godzilla: King of the Monsters initially contained Mechagodzilla.
- Robotics. Intelligence: human or machine? Was Apex Cybernetics really building? Unbeknownst to the humans, a gigantic mecha uses an organic mind (particularly Ghidorah's brain tissue) to move.
- Ann Foley said about how Alexander Skarsgard was a pleasure to work with "His ideas were fantastic, and we had a fantastic time as a result of his contributions. When we first began thinking about the character, Alex wanted to do something a little different; he wanted to have a little more fun with it. In order to pay respect to "Lethal Weapon" and "Back to the Future." he came up with the notion of having his character be a lover of '80s films. His vest is clearly influenced by Marty McFly's outfit. I purchased the foundation, and we made modifications to it. Since I wanted him to feel like he'd owned it since the 1980s, we aged it down a little. Even with his footwear, Adidas was kind enough to collaborate with us on the high-top trainers and assist us in obtaining them."
- While Guillerman and Mark Russell haven't heard either name from Team Godzilla, they had the similar discussion when they encounter Mechagodzilla in the novelization, even if they hadn't heard either name from Team Godzilla.
- As a tragic remembrance of his wife's death, Bernie Hayes keeps a flask of booze in his house, which he uses to short circuit the satellite uplink control panel for Mechagodzilla, allowing Godzilla and Kong one final chance to destroy him.
- Baraka and Nozuki were other names for Warbats.