Marvel Cinematic Universe fans who have been a bit taken aback by the Incredible Hulk’s strange behavior since Thor: Ragnarok, take heed. You’re not alone. One enterprising fan theorist has taken all of the evidence at hand and come to a damning conclusion -- Hulk has not been Hulk since before Thor: Ragnarok.

Instead, Hulk (and Bruce Banner by default) is actually a Skrull, the green-skinned alien shapeshifters who will be introduced into the MCU with Captain Marvel… if they haven’t been toiling in the shadows already. For a little background, the Skrulls were officially introduced to the Marvel Universe in Fantastic Four #2 in 1962. The green aliens are one of the dominant forces in the universe, excelling at invading alien worlds and seamlessly blending in via their ability to change form and adopt new personas. Essentially, they're masters of disguise.

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With that in mind, the fan theory is a fairly long read, but there are some key points worth zeroing in on. The first, most noteworthy point is that, since Thor: Ragnarok, Bruce Banner has exhibited a suspiciously selective memory:

From there, Reddit user Kilgrave theorizes that Hulk lost to Thanos (and nearly lost to Hela’s wolf Fenris) because he is a Skrull who has merely been shapeshifting into the Hulk without the benefit of the hero’s formidable strength. If that’s the case, said Skrull gathered some valuable intel on human civilization in Avengers: Infinity War.

He learns about the Sanctum Sanctorum, chats with Tony Stark, watches Spider-Man do his thing, get access to the Avengers facility, sees some seriously secret Wakandan technology and spends some quality time in the Hulkbuster. That’s some decent information if you’re planning on invading Earth.

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The theory goes deeper into how the Skrulls captured Hulk and why he ended up on Sakaar. It also posits that Skurge is a Skrull, too, working with the Hulk Skrull to get him to Earth. It’s definitely worth a read if you’re looking to rationalize the Hulk’s strange MCU performance as of late. Who knows, this theory might just bear out to be true.

Directed by Taika Waititi, Thor: Ragnarok stars Chris Hemsworth as Thor, Tom Hiddleston as Loki, Cate Blanchett as Hela, Idris Elba as Heimdall, Jeff Goldblum as Grandmaster, Tessa Thompson as Valkyrie, Karl Urban as Skurge, Mark Ruffalo as Bruce Banner/Hulk and Anthony Hopkins as Odin. The film is available now on Digital HD, Blu-ray and DVD.