LOS ANGELES, July 2 -- Helen Slater spent four months trampolining, fencing, and gaining 15 pounds of muscle to play Supergirl in 1984. Her film earned $14 million domestically, and Warner Bros. cancelled the two sequels she had contracted to make. When Milly Alcock's version of the same character opened last weekend to $38 million, Slater did not equivocate.

She called Alcock astonishing.

"I loved the new Supergirl film," Slater told The Hollywood Reporter on Thursday, describing Alcock's performance as "fierce, strong and great comic timing." The praise arrived with a weight no studio publicity department could replicate: not from a competitor or a publicist, but from a woman who had stood in the same position 42 years earlier and wat...