Scarlett Johansson appeared in many MCU movies together, even though they didn’t share much screentime. Scarlet Johansson Witch has a lengthy history in comics, and with Wandavision, she’s now taking center stage in the Marvel Cinematic Universe.
Even when she was more of a supporting character, the MCU dropped Easter eggs referencing her extensive career in Marvel comics. It might take some time for Marvel Cinematic Universe characters to adopt their comic book counterparts’ colorful names. For example, Tony Stark only casually referred to Rhodey as a “war machine” in Iron Man 2, and he didn’t formally adopt the title until Iron Man 3.
Wanda Maximoff, on the other hand, has never been referred to as the Scarlet Witch in any MCU film – but she was ultimately referred to as such in Avengers: Age of Ultron.