The couple was spotted backstage as guest host Melissa McCarthy was taking an audience member on a tour of the New York studio where the sketch-comedy series is taped.
"Hi! Oh, my God! Oh, my God! Ryan Reynolds and Blake Lively," McCarthy exclaimed. "What are you guys doing here?"
"You invited us," Reynolds told her as Lively nodded.
"Yes, yes, I did," McCarthy replied, looking confused. "I said: 'You want to watch it from back here. These are the good seats.'
"I may have been drinking when I invited them," she confessed as she walked away.
Cast member Leslie Jones snapped a selfie with Lively and Reynolds during their visit and posted it on Twitter.
The episode ended with Steve Martin and Alec Baldwin presenting McCarthy with a special jacket commemorating McCarthy's fifth time hosting SNL. The show also saw McCarthy reprise her impression of White House Press Secretary Sean Spicer. This time around, the flustered official was seen driving a motorized podium around Manhattan, looking for Donald Trump after hearing the president planned to fire him.