Jimmy Fallon is hosting 'SNL' on Saturday, Dec. 21, with his BFF Justin Timberlake as the musical guest. In the promos, he hangs with Kenan Thompson, who impersonates the Lake, wears an ugly holiday sweater and throws snowballs at Fallon, making him cry! It's a true LOL set of skits.

Fallon and Thompson filmed the promos atop an NYC skyscraper, with the snow (or is it pigeon droppings?) falling on their heads, scarves and jackets.

Their impromptu version of 'Mirrors' at about 1:30 in is brilliant. It's also very Fallonian and Timberlakian, which we are expecting more of...live from New York, on Saturday night! The Fallon x Timberlake combo is always a winner.

Fallon takes the action inside with cast member Kate McKinnon, as they deliver their horrible acoustic song about the Lake being the musical guest and the general fun to be had this coming weekend.

It's so bad that it's actually really awesome, especially the "leg up for the Christmas show" part. Hilarious!

We're shocked that Fallon got through the promos without laughing, since he is famous for busting out into giggles, mid-skit.