Last year's Superman ended with Iggy Pop singing "Because I'm a punk rocker, yes I am" — an ironic coda for a superlatively square hero. But it rings straightforwardly true for Superman's cousin. Milly Alcock's Kara Zor-El, or Supergirl, sports not a spandex suit but a Blondie T-shirt. When we meet her in Craig Gillespie's Supergirl, she's been on an interstellar bender for days. She's more Courtney Love than Clark Kent.

Nonchalant and sarcastic, Kara is also a little Han Solo-ish, you might say, given that she moves capriciously through the galaxy in her junky spaceship while getting in fights in extraterrestrial bars. She's a welcome, jagged riff on more buttoned-up superheroes, and Alcock is terrific in the role. If only Supergirl were as good as she is.

While the latest DC release, and the second under James Gunn's stewardship, has its moments, Supergirl struggles to match Kara's punk-rock energy with an equally spirited supporting cast and story.