SPOILERS ahead for Dark Phoenix and Captain Marvel!
The greenish, shape-shifting alien villains of Dark Phoenix are referred to in the new (and final) X-Men movie as the D’Bari, but they’re not really like their Marvel Comics counterparts at all. That’s because, according to Dark Phoenix actor Tye Sheridan, they were originally Skrulls. Yes, the same shape-shifters who played such a significant role in the recent Captain Marvel movie.
Source: IGN.com Dark Phoenix Villain Aliens Were Originally Skrulls