Avengers and X-men watch

The X-men and avengers (as well as the Guardians of the galaxy and others in the MCU, you get it) have crashed into a theater, and somehow Peter Parker knows Peter Maximoff? How will the avengers and X-men react to Peter Parker going to/ being from another universe? How will Wanda react to basically having a second brother? And how will pietro react to another version of himself? As well as Erik having some explaining to do.