Superman & Batman Officially Exist in the MCU!
It's true, hard to believe because of all the rivalry (mainly between fans but not the actual companies) but Batman & Superman, and probably the DC Universe actually exists in the Marvel Cinematic Universe.
But maybe not in the way you're thinking. They're referenced by the characters more than once, as Phastos's son claims he saw Superman on the TV shooting laser beams out his eyes, to which Ikaris responds that he doesn't wear a cape. Phastos then sarcastically asks Ikaris if he should call him Clark instead.
At another point, Gilgamesh is asked if he's Thena's butler. To which Gilgamesh compares the remark to Alfred, Batman's Butler.
As a fan of both universes this was fun to hear. Director Chloe Zhao comments on the references:
"I take responsibility for that,"You write it on the page, show it to Kevin [Feige, Marvel Studios President], if he doesn't say anything, that's a go," Zhao added. "I don't think there was a conversation. Not really, except, he goes, 'Oh, that’s cool.'"
We're playing on a genre that draws so much from mythology, and Superman, for example, was created in the comics and also by these brilliant filmmakers along the way – they're modern reinterpretations of a mythical characters that exist in different cultures," Zhao explained. "Ikaris is our interpretation of it. It doesn't mean we can't pay tribute to the really iconic version that we've all grown to love and has influenced us."
It's hard to tell to what level they exist in the MCU, but it could be comics or even movies. Does the Snyder Cut exist in the MCU? MIND = Blown!!
If it comes to a surprise, it hasn't been the only mention in Marvel. Deadpool used Superman's theme song in a Deadpool 2 promo video as he got changed into his outfit in a phone booth. He also jokingly told Cable:
"I'm Batman." and responded to his death threats with "Wow...so dark, are you sure you're not from the DC Universe?"
Titans Season 1 also responded to this dialogue by referencing it in their teaser trailer.
Also, over in the CW-verse, The Incredible Hulk, Spider-Man and The Avengers Age of Ultron get a reference in some episodes of The Flash & Arrow cross-overs.
Who doesn't love a bit of superhero unity hey!