The following article provides spoilers for Episode 1 of She-Hulk: Attorney At Law. Banner is close to Jennifer Walters (Tatiana Maslany) because they are both cousins, and he plays a major role in her transformation as She-Hulk.
Bruce was always haunted by the Hulk's suffering throughout his career in Marvel Cinematic Universe. In Avengers: Age of Ultron, Wanda Maximoff (Elizabeth Olsen) took over his mind, leading to a confrontation with Iron Man (Robert Downey Jr.) that nearly destroyed half of South Africa. In Avengers: Endgame, it was revealed that Banner managed to combine his mind and the Hulk's powerful strength.
Banner set up a lab in Mexico during the five-year gap between Avengers: Infinity War and Endgame, and he worked on bringing his two personalities into one. He takes Jennifer after her first Hulk-out, as she has more of a grasp on Banner's abilities when she attacks him halfway across the island!
Banner appeared with Captain Marvel (Brie Larson) and his father Wenwu (Tony Leung) to discuss the Ten Rings that Shang-Chi (Simu Liu) and his father Wenwu (Tony Leung) wore in Endgame. The device broke during the car accident, allowing Banner to recover his broken arm, as well as his injury sustained while wearing the Infinity Gauntlet.
The reason for the car crash is related to Banner's time on Sakaar during Ragnarok, as the ship is very similar to the one that he and Thor used to escape the gladiatorial planet. And for Hulk lovers, that may hint at a potential Planet Hulk film or TV series.
On Disney+, She-Hulk: Attorney At Law premieres with new episodes every Thursday.