Something you never realised about Guardians of the Galaxy. This is epic.The problem, apart from clickbait headlines being a problem in general, is that realise is what's called a factive verb. That means that whatever is 'realised' should be a true fact. In this case, it's 'something about Guardians of the Galaxy'. Perhaps some hidden in-joke, or an 'easter egg', or trivia about how the film was made.
Compare these examples, taken from Wikipedia and modified by me, where the # means that it's pragmatically weird (doesn't make sense) to say the second part:
Marc realised that he was in debt...With these, which are non-factive and can be cancelled without it sounding contradictory:
#...although in fact he wasn't in debt.
Eliza regretted drinking John's home brew...
#...and in fact she didn't drink it.
Marc thought he had scored full marks...The thing that is realised or regretted must be true, while the thing that is thought or believed might not actually be true, as long as the person thinks or believes it (they may be mistaken).
...although in fact he had got two questions wrong.
Eliza believed she was the winner of the race...
...but in fact she had come second.
This particular post is someone's personal story, and they freely say that it's not based on any factual knowledge, just on their own personal experience of the film. This isn't a fact that we might possibly have realised, so this headline is not only annoying, it doesn't even make sense, and whoever wrote it is now on my List Of People To Tut At Should I Ever Meet Them.