Surprise! Watch Jay Leno's Unexpected Return to The Tonight Show

Guess who's back? Jay Leno just can't stay away from The Tonight Show. The former host returned to his old stomping grounds to tag in for Jimmy Fallon during the monologue portion of the show. It's weird to see him reclaim his old spot and rail on presidential candidates. Ah, the old times! Leno also recently revealed why he didn't appear on Letterman's finale. Watch the clip above to get a dose of late-night nostalgia!