It's practically impossible to throw a virtual stick these days without hitting a Marvel fan theory someone has posted on the internet. The most popular media franchise in the world (with arguably the most dedicated fan base) is guaranteed to produce pages and pages of fan speculation directed at characters like Spider-Man and the Avengers. However, one branch of the Marvel Cinematic Universe has a greater scope - and more opportunity for theorizing - than the rest of them, and that's led to oodles of Guardians of the Galaxy fan theories popping up all over social media.
Theories about Guardians of the Galaxy range from making sense of the ambiguous backstories of the central cast to the bigger mysteries hiding in that galaxy not so far away. Director James Gunn has done such a remarkably thorough job of world-building in these films that it allows fans to enjoy the tantalizing feeling their speculation may actually uncover some hidden and intentional secret.
The character of Mantis is one of the more obscure Marvel properties out there, but she quickly became a fan favorite after Pom Klementieff’s adorable portrayal in Guardians of the Galaxy Vol. 2. In fact, Mantis is such a fan favorite that many ignore the fact she’s actually complicit in Ego’s murdering of dozens of his own progeny. It wasn’t until her new friends, the Guardians, were in danger that Mantis acted against Ego, but Redditor/u/Petronella23 thinks they know why that is.
Mantis decides to warn the Guardians after a scene in which she touches Drax while he is reminiscing about his daughter and feels his extreme sorrow. Redditor/u/Pentronella23 theorizes it was in this moment Mantis learned normal people don’t callously slaughter their children and are actually meant to care about them - which led to her sudden realization that what Ego was doing was seriously messed up.
There are a number of dark twists in Guardians of the Galaxy Vol. 2, but the fact Ego has been slaughtering his own children for centuries is certainly among the darkest. Ego had been on a lifelong quest to sire a child with the “Celestial gene,” but failed every time - until he met Peter Quill. For some reason, Quill had the Celestial gene and access to Ego’s powers, and Redditor/u/DrArgumental speculates Yondu Udonta is the reason why.
All of the rest of Ego’s children were delivered to him at a young age and then killed when they proved useless to him. Quill, on the other hand, was rescued from this fate by Yondu, which allowed him to grow to adulthood. DrArgumental theorizes the Celestial gene becomes active sometime during puberty, and Quill was simply the only child of Ego allowed to live long enough to gain Celestial abilities.
On at least two separate occasions, audiences witness Baby Groot immediately halting his joyful dancing when Drax is looking at him, but it’s never made explicit why he does this. Redditor/u/LtCommanderCarter thinks the reason Groot doesn’t want Drax to see him dancing is rather simple - he knows about Drax’s disdain for dancing, and doesn’t want to upset his friend.
As LtCommanderCarter says, “Groot does this because he wants Drax to love and respect him. Drax talks about his deceased wife in GotG 2 and notes that she never danced and that was a good thing. Not giving into the frivolity of dancing is a positive attribute in Drax's eyes; thus Groot does not let Drax see him dance.”
Long-time readers of Marvel Comics know Star-Lord and the gang aren’t the original Guardians of the Galaxy - the team name was first used by a group of superheroes from the year 3000. Guardians of the Galaxy Vol. 2 revealed a version of these original Guardians, headed by Sylvester Stallone’s Starhawk and formerly featuring Yondu Udonta, who was permanently exiled. Redditor/u/JokerFaces2 theorizes audiences will get to see this Ravager team in action in Guardians of the Galaxy Vol. 3 via extensive flashbacks.
As an added bonus, this would allow for the return of Yondu, and that means Michael Rooker. To date, director James Gunn has yet to direct a movie without Rooker in it, so why would he want to start now?