As the Avengers—consisting of Stark, Banner, Steve Rogers (Chris Evans), Thor (Chris Hemsworth), Natasha Romanoff (Scarlett Johansson), and James Rhodes (Don Cheadle)—face off against Ultron, they are joined by new allies: Pietro (Aaron Taylor-Johnson) and Wanda Maximoff (Elizabeth Olsen), twins with superhuman abilities, and Sam Wilson (Anthony Mackie), a.k.a. the Falcon. This expansion of the team brings fresh dynamics and challenges, testing the original Avengers' cohesion and their understanding of what it means to be a hero.