Jimmy Fallon taught me that in Greek, nostalgia literally means "the pain from an old wound." It's a twinge in your heart far more powerful than memory alone. This device isn't a spaceship, it's a time machine. And last night on The Tonight Show, Fallon loaded up that time machine with old SNL pals Horatio Sanz, Chris Kattan and Tracy Morgan to perform their holiday classic "I Wish It Was Christmas Today," with special guest Ariana Grande.

Reminder: "I Wish It Was Christmas Today," which the foursome first played on SNL way back in 2000, was supposed to be a purposefully-bad/purposefully-goofy Christmas song. Except, as with all things nostalgia, it's actually become beloved in its own right over the intervening 18 years.

Fallon, Sanz, Kattan and Morgan have reunited many, many, many times over the years to perform the song, including in 2004 with The Muppets. And guess what?!?! You can watch all of them below:

Julian Casablancas made a pretty rockin' version of it too: