WHO? In the comic books, the Invisible Girl (a.k.a. Sue Richards) is the wife of team leader Mr. Fantastic, and the wise, steady matriarch of the Fantastic Four clan. Along with the rest of the team, she got her powers after an ill-fated trip into space showered the foursome with ''cosmic rays.'' That origin seemed logical enough in 1961, but expect it to be updated: One possibility is contained in the new ''Ultimate Fantastic Four'' series, which has the team get its powers in a disastrous teleportation experiment.
SUPERPOWERS Duh. Sue's able to turn herself transparent, making her as hard to find as good reviews for ''The Hulk.'' But she can also project invisible force beams, so look for Alba to spend much of the film perfecting an ''I'm using my powers'' squint, à la Famke Janssen in ''X-Men.''
RIGHT FOR THE ROLE? Twenty-three-year-old Alba looks little like the comic book character, who's a blonde soccer mom. But her fetching screen presence and familiarity with comic-book-style action (she WAS Dark Angel!) should overcome any doubts.