The Rams' huge win didn't go off seamlessly on Sunday ... 'cause the Jumbotron operator at their stadium mistook Big Sean and Jhene Aiko for Sarah Michelle Gellar and Freddie Printz Jr. -- and the scene was hilarious.
Just before L.A. beat the San Francisco 49ers to advance to the Super Bowl at SoFi Stadium ... someone really screwed up as the camera was panning around to celebs in the crowd.
When it got to Big Sean and Aiko ... the graphics below them read "Sarah Michelle Gellar" and "Freddie Prinze Jr.