The MCU is very fond of the multiverse these days, but no other movie has embraced it quite like “Doctor Strange in the Multiverse of Madness.” It devotes plenty of time to explaining the concept and illustrates the idea by taking the viewer to several curious alternate-universe locations. These include Earth-838, where we meet the Illuminati — a team consisting of veritable Marvel all-stars like Reed Richards (John Krasinski) and Captain Carter (Hayley Atwell). The Illuminati also gives us the first MCU movie appearance of X-Men founder Charles Xavier (Patrick Stewart), who also gets a name-drop in “The Marvels” mid-credits scene.
If the viewer is familiar with “Multiverse of Madness” and the ground rules of the MCU multiverse, they have a much easier time understanding the ending of “The Marvels.” After all, knowing about the Illuminati and various alternate versions of folks like Stephen Strange (Benedict Cumberbatch) makes it far easier to understand that the place Monica becomes stranded in after closing the hole Dar-Benn (Zawe Ahston) tears in time and space is simply another universe.
Granted, “Multiverse of Madness” is far from the only MCU project that references alternate universes. Disney+ shows “What If…?” and “Loki” are all about the multiverse, and it also features heavily in both “Spider-Man: No Way Home” and “Ant-Man and the Wasp: Quantumania.” However, the “Doctor Strange” sequel is the only MCU movie that devotes its entire runtime to different universes and the many versions of well-known Marvel characters they contain. Since this is incredibly important for the current MCU and “The Marvels” doesn’t really bother explaining it, this makes “Multiverse of Madness” essential viewing before watching the movie.