Warning: Full spoilers follow for Dark Phoenix.
If you don’t want to know about this big X-Men Easter Egg in the film, read no further! But head in this direction if you’re wondering whether or not Dark Phoenix has a post-credits scene.
Fox’s X-Men movie universe may be coming to a close, but not before debuting one last fan-favorite character. Dazzler finally makes her big screen debut in Dark Phoenix, albeit only in cameo form and apparently played by Halston Sage (The Orville). She has no dialogue but is seen singing — and using her mutant powers to generate a light show while wearing her trademark white outfit — during the X-Men’s party on the grounds of the mansion.
Source: IGN.com The X-Men Movie Franchise's Last Great Mutant Easter Egg