On Halloween you can become anyone you want, and last night on Jimmy Kimmel Live fill-in host Dave Grohl became old, bearded David Letterman, while guest Kristen Bell dressed as Tom Selleck’s Magnum P.I. But their role-playing didn’t end with their costumes, because the two then rocked out to Frozen‘s “Do You Want to Build a Snowman,” which—midway through—turned into Metallica‘s “Enter Sandman.” Enter Snowman. After Grohl—who looked so much like the current grizzly version of the retired late night host you would have thought it really was Letterman—told Bell it was “the biggest deal” to his kids that he was sitting with Princess Anna, and that if he “jammed” with her it would make him the coolest dad. Bell, naturally, then got up and dedicated her song from Frozen to his daughters. But when Grohl got on the drums, the intensity picked up and suddenly the duo became a pretty entertaining Metallica cover band. Huge bonus points here too for the rest of the band’s amazing famous musicians from the ’80s costumes.Did we need a Frozen/Metallica mashup? Probably not, just like we probably didn’t need to eat 40 pieces of candy last night either. But that doesn’t mean we didn’t enjoy that, too. Sometimes you just have to indulge in the moment though. Like dressing up as a famous talk show host to fill in for another talk show host, before playing the drums while Frozen‘s Princess Anna sings a Metallica song while dressed as Magnum P.I. What could be more Halloween than that? [mpx_video type=”alpha” guid=”_cWsvzPM8Ujcu9oq6_7J_H5g3Bdr3W7d”] No, seriously, how could this possibly have been more Halloween? This is like Halloween-Inception. Whose costume here was your favorite? Dress up our comments section below with your answer.