The main character/s of the last Yas Forums related media you watched/read is now a part of the One Piece world...

He'd probably be a "creation" of Vegapunk but would be heavily implied to actually just be an alien that Vega accidentally warped to earth.

Minks then. Either way, its doubtful that they will be cooked.

J'onn would just be an alien. Aliens exist in One Piece.