WATCH: Taylor Swift jam with Paul McCartney at the Saturday Night Live after party

Jimmy Fallon spills the goss from the Saturday Night Live after party.

Saturday Night Live's three-and-a-half-hour-long 40th anniversary special aired in the U.S on Sunday – but apparently that was only just beginning.

After the broadcast, pretty much all the stars you'd ever imagine made their way to what has to be one of the most spectacular, star-studded after parties of all time.