How did MCU writers of 'Rogers: The Musical' know Cap's iconic catchphrase & those Avengers secrets?

"Avengers, unite, because we've got to hear you sayyyy: I can do this all dayyyyy!" Be honest, those lyrics from Rogers: The Musical have been stuck in your head for the last month, too, right? There's no shame in admitting it. Just like "Agatha All Along" in WandaVision, Hawkeye cooked up its own earwig-y jam by way of a fictional stage play about the life and times of Captan America.

There's just one thing fans have pointed out over and over again since the latest MCU series debuted on Disney+ in late November: how did the in-universe writers behind the smash Broadway hit know about Steve's famous "I can do this all day" catchphrase when none of them were around to hear it during the handful of times he said it aloud?

Thankfully, one of the real-world lyricists who gave us "Save the City" — Grammy, Emmy, and Tony Award-winning and Oscar-nominated composer Marc Shaiman — recently sat down with Inverse to finally answer that very question. "We talked about that with [Hawkeye director] Rhys Thomas," Shaiman, who wrote the song alongside regular collaborator Scott Wittman, recalled during the interview (though perhaps he meant to name-drop head writer and executive producer, Jonathan Igla).

"We just figured in the universe, people writing a musical or writing a book or writing a magazine article would've done their due diligence and homework and interviewed people who had been there," he continued. "Perhaps, even in things that we've never seen, members of the Avengers had actually given interviews about this or that."

Shaiman admitted that "there was a certain amount of liberty" when it came to the song. "Maybe Natasha in some interview on CNN might have said, 'Oh, you know this guy, he's always like, ‘I could do this all day,'" he mused. "It could have come up somehow. The same thing applies to including lyrics about getting some shawarma when we're done. I wrote these things and no one objected to them! But we did talk about that. And we just figured that they don't say these things in a total vacuum. And you know how Marvel people are, you would’ve thought they would say, 'No, no, this isn’t possible.' But from Kevin Feige on down, they were like, 'This is good.'"

Of course, the other elephant in the room is the fact that Rogers: The Musical tries to claim that Ant-Man was present for the fight against Loki and his Chitauri army when the character wasn't introduced into the MCU until three years later. "That came from Rhys and Marvel, as something to further aggravate Hawkeye as he watched the show, and also as a comment on how movies and articles and people always get something wrong," Shaiman revealed (again, it's unclear if he meant Igla in this instance).

Briefly glimpsed in the Hawkeye season opener, the big musical number dedicated to the Battle of New York was shown in its entirety via a mid-credits scene that plays at the end of Episode 6. This may have left some audience members a tad crestfallen, as many fans were hoping for more character teases following the reintroduction of Vincent D'Onofrio's Kingpin. Even the director of the episode felt a shade disappointed.

All six episodes of Hawkeye are now streaming on Disney+.