The following contains spoilers for Thor: Love and Thunder, now playing in theaters
The world of the Marvel Cinematic Universe is one increasingly defined by superheroes. Within the context of the universe, the revelations brought on by aliens, magic and god have resulted in an entirely different culture -- that increasingly seems to contain one of Marvel's biggest rivals. A minor gag from Thor: Love and Thunder reference the work of Christopher Nolan -- and after a previous confirmation that the DC Universe exists in the MCU, this seems to suggest that his Dark Knight trilogy might exist as a popular film series in the MCU.
Early in Thor: Love and Thunder, audiences are reintroduced to Jane Foster while she's taking chemotherapy for her cancer. While going through the process, she ends up next to another patient who's actually reading the book she wrote about the kind of sciences she encountered thanks to her history with Thor. While trying to explain the specifics of how advanced space travel works, Jane compares it to Interstellar -- Christopher Nolan's 2014 sci-fi film starring Matthew McConaughey and Anne Hathaway. She even notes that it serves as a pretty accurate explanation of high-minded scientific ideas.
This seems to imply that within the context of the MCU, Christopher Nolan exists and is a filmmaker as he is in the real world. Interstellar came about thanks in large part to his previous successes -- such as The Dark Knight trilogy starring Christian Bale. The DC Universe has also been confirmed to exist in this universe, with Phastos' son in Eternals comparing Ikaris to Superman.
Given that Nolan's successes with the Batman films helped establish him enough for Warner Bros. to invest in his later films like Inception and Interstellar, it stands to reason then that he had similar successes in the MCU. Put together, this suggests The Dark Knight trilogy of Batman Begins, The Dark Knight and The Dark Knight Rises actually exists as a popular film series within the MCU.
The Dark Knight trilogy existing in the MCU invites a lot of questions, specifically how a universe of heroes like Iron Man, Captain America and Spider-Man perceives The Dark Knight. This isn't the first time Marvel characters have referenced Batman, either -- with Spider-Man overtly referencing The Dark Knight during a cameo appearance in Runaways.
The Christopher Nolan movies specifically invites a lot of possibilities, and how characters perceived the series. Iron Man likely saw an idealized tragic version of himself in Bruce Wayne, and definitely defended his shadier tactics. Meanwhile, Captain America is likely bothered by those same tactics. There's no way a movie nerd like Spider-Man doesn't also have a lot of opinions on the movie.
There's even a good chance the movie's cultural impact meant villains got the chance to see it. Shang-Chi and the Ten Rings' Wenwu could have seen similarities between his Ten Rings organization and Ra's al Ghul's League of Shadows from Batman Begins. Meanwhile, Iron Man 3's Aldrich Killian may have based his version of the Mandarin somewhat on the Joker persona created by Heath Ledger. Even Black Panther's Killmonger likely sees the appeal of someone like Bane -- and works to not fall for the same things that doomed his own scheme.
As the world's big superhero publishers, Marvel and DC have long inspired and replicated each other's successes. However, it's always funny to consider how their impact on each other's universes might actually apply in-universe -- and a throwaway gag from Thor: Love and Thunder might have found a way to quietly make a version of Batman canon in their universe.