If you've turned on a television, taken a subway, or watched a YouTube video over the past month, you've probably seen a Gillette ad asking, "How Does Superman Shave?"

For the extensive campaign, which is tied to Friday's Man of Steel, the company reached out to multiple celebrity Superman fans — but somehow missed Jerry Seinfeld — in an attempt to solve the mystery. It's a nerdy but intriguing question: If Superman is impervious to knives and bullets, how can any standard Earth razor stand up to his super-stubble? The question gains even more relevance with Man of Steel, which sees a young Superman with a full, bushy beard for an extended portion of the film.

The only problem? Fans already know how Superman shaves: He concentrates his heat vision, reflects it off a mirror, and aims it back at his face, burning off the stubble. The Superman Wiki features an impressively exhaustive collection dedicated to documenting the Man of Steel's shaving routine. In 1960, Superman #139 featured a bearded Superman asking his Kryptonian allies Supergirl and Krypto the Superdog to use their heat vision to burn his whiskers off. (It was a strange time.) In 1986, The Man of Steel #4 offered a weirdly detailed inner monologue in which Superman thinks through his long, elaborate shaving routine over three panels. The method has even been depicted on TV before; here, watch the Man of Steel employing the unique grooming method in two separate Superman stories — Lois & Clark and Superman: The Animated Series:

In Gillette's defense, Kevin Smith acknowledges the canonical heat vision explanation in his ad-campaign video before dismissing it as implausible. "I didn't buy it then, I don't buy it now. I think there are better theories to look at," he says before offering his own take (which is, for the record, that Superman shaves with a piece of the advanced spaceship that originally brought him to Earth). And canonical or not, the heat vision theory comes with its own problems; if Superman's heat vision is powerful enough to vaporize an entire army of Doomsday replicas, why can't it burn through a standard Earth mirror?

Still, Gillette's "How Does Superman Shave?" campaign demonstrates the difficulty of marketing to fans who are very, very familiar with all the intricacies of Superman's powers. Typing the promotional hashtag #HowDoesHeShave into Twitter reveals dozens of tweets from Superman fans grumbling that we already know the Man of Steel's shaving routine. Then again, grumbling is still some level of engagement...

If you'd still like to see celebrities offering their own unique (and canonically incorrect!) explanations for Superman's shaving routine, well, here they are:

1. Bill Nye — The "Materials Science" Theory

2. Kevin Smith —The "Kryptonian Rocket That Brought Superman to Earth" Theory

3. Mayim Bialik — The "Enyzmatic Follicle Denaturation" Theory

4. Jamie Hyneman and Adam Savage — The "Large Hadron Collider" Theory