Fallon and Timberlake make a history of rap for ‘SNL 40’

One of “Saturday Night Live's” most beloved hosts, Justin Timberlake, and one of its most successful former cast members, Jimmy Fallon, combined again for a very special cold open to the 40th anniversary show last night.

Fallon and Timberlake have formerly knocked socks off with their “History of Rap” series on Fallon's various late night shows, so writers cobbled together some catch-phrase-driven rhymes to help ring in “SNL 40.”

Mary Katherine Gallagher (Molly Shannon) and Debbie Downer (Rachel Dratch) made guest appearances during the cold open musical number — which, should be noted, causes ratings to go down for the show, according to Debbie.

“NBC doesn't care about ratings!” exclaimed Fallon, who is enjoying his NBC slot over at “The Tonight Show.”

Watch the full opening and SNL history spanning intro below.