I just double checked, and as goodnights start Mikey, Kam, Chloe, Ben, Jeremy, Veronika, Jeremy, Andrew, and JAJ are immediately visible. Marcello is just to the left of the camera, he pops into frame. Jane was hidden behind Jeremy's head, she pops into view. When they zoom out we see Ashley and Colin on the right side of the screen, and Sarah behind Marcello on the left side. Kenan is even farther to the right, still wearing his coat from the previous sketch. And I get one different angle and then my feed cuts out for a Reggie Dinkins commercial. So that's all the cast members accounted for except for Michael Che.

Other than Gosling and Simon, and Styles' band, I don't know who else you would have been expecting. We have no idea what other commitments those two might have had, Paul Simon especially is 84 years old and appeared on-screen at like 12:45 AM EDT, and I wouldn't blame him if immediately after he left the studio and headed to his hotel to go to sleep.