Hawkeye episode 1 sees Clint Barton attending a Broadway show, Rogers: The Musical, about The Battle of New York. But why is Ant-Man in it?
Marvel's Hawkeye hilariously incorporates Ant-Man into its first episode, as he features in Rogers: The Musical despite not having been present for the events from The Avengers that the musical covers. Because Hawkeye is one of the original six Avengers, the show features plenty of references to the team, Clint Barton's place on it, and certain key events like The Battle of New York. But the inclusion of Ant-Man in a Broadway musical about the Avengers is a particularly humorous yet poignant error.
Given all that Clint Barton has been through in Hawkeye's MCU timeline, and his tendency to be low-key, seeing him attend a colorful Broadway musical about the events of the first Avengers movie is ironically funny enough. The mistaken inclusion of Ant-Man in Hawkeye's strange Captain America musical further emphasizes the comedy of it and Clint's annoyance with the whole show. It also helps to underscore the numerous ways in which remembering The Battle of New York is painful for Clint, and provides another example of how people who weren't there tend to falsely romanticize the event.
During the musical scene in Hawkeye episode 1, Clint turns off his hearing aid while watching the fake Natasha dance on stage, a pained and distant expression on his face as he no doubt remembers his love for her and the guilt he feels over Black Widow's Endgame death. When his daughter calls him out on it he tells her, "I know what happens. I was there. You know who wasn't there? Is that guy. Ant-Man." Clint's frustration with the show thus exists on multiple levels. For one, it forces him to confront Natasha's memory in a way that clearly saddens him. It also likely brings back unpleasant memories of being manipulated by Loki around the same time, an experience that has weighed on him in the past. Finally, Hawkeye's role in the musical is pointedly small, as he doesn't even get an individual mention during the roll call of all the other Avengers, incorrectly including Ant-Man. Though Ant-Man's anachronistic inclusion in Rogers: The Musical doesn't directly relate to any of this, it acts as a focal point for all of Clint's other frustrations, as well as effectively delivering a moment of Marvel's signature comedy in the face of deeper emotion.
Clint's comical annoyance with Rogers: The Musical's cheesiness and cluelessness, which Ant-Man's presence serves to highlight, is also one more way in which Hawkeye calls out the way people tend to romanticize the Avengers' battles. Kate's obsession with Hawkeye, her desire to improve his "branding," and to become a hero just like him, all stem from seeing him in action during The Battle of New York and assuming that the superhero gig is far more glamorous and fun than it really is. But as Hawkeye tells Kate Bishop, a superhero life "comes with a price," something he knows all too well. Hawkeye episode 1 is even titled "Never Meet Your Heroes." The irony of Clint watching an Ant-Man actor dance and sing onstage reenacting events he was never there actually there for is thus not only meant as a comic pay-off, but also as an illustration of the disparity between how the world sees superheroes, and how Clint Barton sees himself. This is why Rogers: The Musical, with its funny Ant-Man mistake, is both a comedic and meaningful addition to Hawkeye's story and themes.