Kristen Bell and Dave Grohl mashed up Metallica and 'Frozen' and it kind of worked

Do you want to build a... Sandman?

Taking over for Jimmy Kimmel on Halloween night, Foo Fighters' Dave Grohl, dressed as a beardy David Letterman, was chatting with Frozen star Kristen Bell, dressed as Tom Selleck.

After asking Bell to "jam," she dedicated the Frozen hit "Do You Want to Build a Snowman?" to Grohl's kids, Violet, Harper and Fifi — officially making him the "coolest dad."

Grohl jumps on the drums and the whole thing tumbles into Metallica’s classic "Enter Sandman." It kind of works. But, who cares? It's Halloween.