"Saturday Night Live" is gearing up for its epic 50th anniversary, and it's shaping up to be a spectacular episode ... 'cause a bunch of superstars were spotted rolling in for rehearsals.

The guest list is insane -- we’re talking Wyclef Jean, Nick Carter ... and Cher herself!

The whole Backstreet Boys crew showed up Wednesday night in NYC, with Kevin Richardson and Howie Dorough bringing that Larger Than Life energy to the party. Check out the gallery with last night's arrivals!

"SNL" vet Maya Rudolph was all about coming home -- seen making a chill entrance for what’s sure to be a big splash on our screens this weekend.

Cecily Strong, another former "SNL" alum, was back to join the celebration of a show that's been defining TV talent since '75. Talk about a legacy!