The X-Men have arrived in the Marvel Cinematic Universe, or at least have begun to. The Marvels' mid-credits scene features the appearance of Kelsey Grammer's version of Beast, greeting Monica Rambeau as she arrives in an alternate reality, firmly linking the 20th Century Fox X-Men franchise to the MCU for the first time. Considering that Disney purchased Fox more or less to get the rights to Marvel's Merry Mutants, it's a watershed moment for the saga.
Source：https://www.cbr.com/the-marvels-mid-credits-scene-x-men-continuity/
