Trivia: There is a persistent rumor that Daniel Craig was going to have a cameo as a member of the Illuminati. Craig allegedly would have played Balder the Brave, a sibling of Thor. While it has not been 100% confirmed, reports suggest Craig was cast in the role, but ultimately dropped out due to a sudden rise in COVID cases during the film's production. (He didn't want to risk travelling and getting his family sick.) Thus, the character was simply written out and replaced with another Marvel hero.
Trivia: The identity of the film's main antagonist was the subject of much speculation in the months leading up to its release. Nightmare was rumored, and the release of a toy line for the film showed action figures for the characters Sleepwalker and D'Spayre, neither of whom actually appear in the film.
Trivia: The six members of the Illuminati in the film are Mordo, Maria Rambeau, Captain Carter, Reed Richards, Professor X, and Black Bolt. The latter three are also members in the comics, however, the other three slots in its original incarnation were occupied by Doctor Strange, Namor, and Iron Man.
Trivia: SPOILER: This marks the first appearance in film for a member of the Inhumans, with Black Bolt being a member of the Illuminati. The Inhumans were originally supposed to have their own movie as part of the MCU's phase 3, but it was scrapped and adapted into a negatively received TV series on ABC, which was canceled after one season. Anson Mount, who plays Black Bolt here, also played Black Bolt in the TV series.
Trivia: After 22 years and a dozen film appearances, this is the first time Professor X is shown using his iconic gold hoverchair from the comics and 90's X-Men animated series. He is also wearing a green suit jacket with a black and blue tie, which were what he wore in the aforementioned series.
Trivia: SPOILER: This is the first MCU film to feature characters from Fantastic 4 and X-Men (Scarlet Witch and Quicksilver's association with X-Men in the comics notwithstanding). These properties were previously unavailable to Marvel Studios, as their film rights were held by Fox prior to their acquisition by Disney in 2019.
Trivia: Patrick Stewart revealed in January 2021 that he had conversations with Marvel Studios President Kevin Feige about reprising his role of Professor Charles Xavier in the MCU. Stewart claims to have declined, reasoning that he felt his appearance in Logan was a fitting end to his time as the character, but it appears that he was either fibbing, or later changed his mind.
Trivia: SPOILER: Prior to his appearance here, John Krasinski was a popular fan pick to portray the MCU version of Reed Richards/Mr. Fantastic. His wife Emily Blunt has also been a popular fan pick to play Reed's wife Susan Storm/Invisible Woman. Blunt has said the role does not interest her, but actors in past MCU projects have been known to mislead about their involvement.