Marvel's upcoming "Moon Knight" series, starring Oscar Isaac and Ethan Hawke, is currently filming in Budapest, and thanks to the wonders of social media, we now have confirmation that another major MCU actor, Mark Ruffalo — the Hulk himself — has been sighted in the same neighborhood. Could the Hulk be making an appearance in "Moon Knight?"

Isaac and Ruffalo each posed for a picture with Instagram user Dora Magyari outside the same Budapest hotel, which is being used as one of the main shooting locations for "Moon Knight." It's possible that Ruffalo was just visiting the set, but he later sent out a cryptic tweet linking to a ScreenRant article with the photos embedded.

Here's the tweet, so judge for yourself:

Ruffalo's tweet alludes to him getting in trouble for being loose-lipped about future developments in the MCU. Looper even compiled a list of every time he's let an MCU spoiler slip. He says he's learned his lesson, but at the same time, linking to that article would seem to tease that he is involved in "Moon Knight," somehow. Or maybe he's just having fun?

But what exactly does he mean by saying he's "the person who's responsible for this next phase of the MCU?"

The Stairs To The Multiverse

It seems like what Ruffalo is referring to there is the creation of the multiverse, which came about as a result of the Hulk taking the stairs instead of the elevator in "Avengers: Endgame." If you remember, the Hulk came bursting through the door in the lobby of Stark Tower, knocking the future, time-traveling Tony Stark on his ass, and causing him to drop the Tesseract. Loki promptly snatched up the Tesseract and teleported into his own Disney+ series, which subsequently introduced the multiverse into the MCU (or the Marvel Cinematic Multiverse, as we may soon need to start calling it.)

We already knew that Ruffalo would be showing up alongside Tatiana Maslany and Jameela Jamil in Marvel's "She-Hulk" series. The character of Bruce Banner, AKA Hulk, has a lot of comics history with Jennifer Walters, AKA She-Hulk, since he's her cousin. Hulk doesn't have that same history with Moon Knight, however, so if indeed he does show up in the "Moon Knight" series on Disney+, it will be interesting to see how they fit him in.

Because Universal Pictures holds the distribution rights for the Hulk's solo movies, we haven't seen one of those since "The Incredible Hulk" in 2008. That was before Disney bought Marvel Studios and Ruffalo took over the role from Edward Norton. Unless Disney and Universal are able to work out some kind of deal like Marvel has with Sony and Spider-Man, then it seems like having the Hulk as a co-star or guest star in movies and TV shows is the best we can hope for.

"Moon Knight" hits Disney+ in 2022.

Read this next: 'Moon Knight' Star Oscar Isaac Teases A Series That Doesn't Follow Typical Superhero Logic

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