On October 30, 2005, the Bengals faced Brett Favre and the Green Bay Packers at Paul Brown Stadium in Cincinnati, Ohio. The Bengals won the game but that isn't what is remembered. Favre threw five interceptions but that isn't what is remembered either.
What folks remember is the fan who ran out onto the field and stole the ball from Brett Favre during the game's final drive. With 23 seconds to go, the fan got onto the field. He made his way to the Packers quarterback. When he got there, he took the ball from Favre who was trying to lead his team to a game-tying score.
These slides were taken from a Powerpoint that went viral back in 2005.