Mark Ruffalo has the perfect casting for She-Hulk in mind; it's just that it's not possible. A few months ago, Marvel head Kevin Feige announced She-Hulk, an MCU-set series planned for the new streaming service Disney+. Marvel already has a plethora of shows planned for Disney+, including The Falcon and the Winter Soldier and Loki. Most of the shows in development follow characters already seen within the MCU, but a trio of newcomers will soon join the mix. In addition to She-Hulk, Marvel is developing Ms. Marvel and Moon Knight for the streamer.
With his role as Bruce Banner, Ruffalo seems like the best choice to have an opinion on She-Hulk's casting. Bruce was one of the heroes to make it to the end of Avengers: Endgame, so there is a chance he could make a reappearance someday. She-Hulk could be a perfect opportunity to feature him again, as in the comics, Jennifer Walters (AKA She-Hulk) is Bruce's cousin and acquired her abilities after getting a blood transfusion from him. It's unclear if the show will keep that origin story, but as She-Hulk recently found its head writer, plot details could be emerging soon.
According to CBR, Ruffalo shared his ideal casting at the SAG-AFTRA Foundation's Patron of the Artists Awards, where he was one of the award recipients. Ruffalo said, "I mean, Tessa Thompson's already Valkyrie but she'd be a great She-Hulk." Ruffalo and Thompson co-starred in 2017's Thor: Ragnarok, where their characters struck up an odd and unlikely friendship. They also shared a brief moment in Endgame.
Thompson would make an excellent She-Hulk, and it would be fun to see her and Ruffalo onscreen together again if he were to make an appearance on the show. However, Thompson's role as Valkyrie means she can't take on another MCU part, especially since Phase Four will already be a big one for Valkyrie. At the end of Endgame, she was crowned "King" of Asgard by Thor, and Thor: Love and Thunder will show her assuming the role. It will also depict her as openly bisexual, making her one of the first LGBTQ MCU heroes.
Marvel hasn't given a time frame for when She-Hulk will be released, so it's unlikely there will be any casting news for a while. While Thompson cannot be cast, there are plenty of other actresses who could fit the role, such as Stephanie Beatriz (Brooklyn Nine-Nine), who has already stated she would love to play the part. The Marvel shows on Disney+ will tie into the films in major ways, which could suggest She-Hulk will someday make it to the big screen. Also, another female-led project for Marvel is an exciting prospect and further shows the recent push the studio has made toward increased diversity. It's still very early to speculate about the directions the show could go in, so for now, fans will just have to wait for more news.