Supergirl is off to a spectacular start on CBS. Boosted by a special lead-in from The Big Bang Theory, Monday’s premiere drew nearly 13 million same-day viewers, making it the most-watched series premiere of what has heretofore been a lackluster fall for both broadcast and cable networks. It also gives Supergirl the distinction of having the broadest opening of any of the recent wave of superhero-themed TV shows: ABC’s Marvel’s Agents of S.H.I.E.L.D. kicked off the recent boom by drawing 12 million viewers back in September 2013. More encouraging for the Eye network is the fact that younger viewers found the show, allowing Supergirl to soar to a 3.2 rating among viewers under 50, the highest-rated series bow in the key demo. (Fun fact: The previous top-rated series premiere this fall among young adults had been NBC’s Blindspot, which, like Supergirl, is from executive producer Greg Berlanti.) One night does not a hit make, of course, and in coming weeks, Supergirl will have to fly solo, without the benefit of a Big Bang lead-in. And it’s worth remembering S.H.I.E.L.D. and Fox’s Gotham also had big first nights, but quickly saw their same-day viewership fall off sharply. For now, however, CBS’s decision to veer outside its usual crime-procedural lane looks like it might have been a wise one.