NFL
By official National Football League rules, players with the numbers 50-79 and 90-99 are ineligible receivers. The quarterback or offensive captain informs the referee that a usually ineligible receiver will be eligible for that play. The referee then announces that the ineligible number "x" is reporting as an eligible receiver. This announcement is made using the referee's microphone so both spectators and opposing team can hear. The eligibility is good for only one play and must be done before every play in which the offense plans on making the player eligible.
The tackle-eligible play typically goes unnoticed, but for one prominent exception: when the player reporting as an eligible receiver catches a forward pass (usually for a very short touchdown).
The name most commonly associated with the tackle-eligible play is Mike Vrabel, a linebacker who recorded 11 receptions for 11 touchdowns in his career—including one each in Super Bowl XXXVIII and Super Bowl XXXIX—as a member of the New England Patriots and Kansas City Chiefs.
Cincinnati Bengals' Pro Football Hall of Fame offensive tackle, Anthony Muñoz caught 7 passes for 18 yards and 4 touchdowns in his prolific 13-year career. Buffalo Bills' offensive tackle, Mitch Frerotte made a name for himself in 1992 by scoring 3 times in one season (twice on tackle-eligible plays), the best single season ever for an offensive lineman.
A widely noted use of a tackle-eligible play came in The Monday Night Miracle when New York Jets lineman Jumbo Elliott caught a 3 yard touchdown pass to cap a 23 point comeback against the Miami Dolphins.
Read more about this topic: Tackle-eligible Play