Origin: Eli Manning's general doofiness and Peyton's association.
Eli's constant childish bewilderment is what popularized the Manning Face despite his older brother's legendary status. After Eli's terrible season got cut short when the Giants missed the playoffs, Peyton continued the tradition by suffering a legendary beat down from the Legion of Boom at the Super Bowl. Stephen A. Smith said the following morning that the Broncos got punked, and Manning certainly looked like it.
22. The Manning Face