Sir Paul McCartney took the SNL stage for the Season 51 finale as musical guest, delivering a live performance of “Help!” that became an instant highlight, and not just for the song. Will Ferrell, hosting the episode, joined in on cowbell, prompting McCartney to break into genuine laughter mid-performance, a moment that sent the internet into full meltdown. Red Hot Chili Peppers drummer Chad Smith anchored the whole thing on drums, and the result was exactly the kind of unrepeatable live television that SNL was built for.