Palpably Unfair Play is an odd term that even some of the most-knowledgable of American football fans may not be familiar with. It was a rule and term that originated out of several specific incidents lost to history and it is consequently now included in most football rulebooks. It also one of the ways or methods in which points can be awarded under certain circumstances, and thus is a good piece of football trivia.
The National Football League (NFL) rulebook defines "palpably unfair play" or a "palpably unfair act" as follows:
A player or substitute shall not interfere with play by any act which is palpably unfair.
Penalty: For a palpably unfair act: Offender may be disqualified. The Referee, after consulting his crew, enforces any distance penalty as they consider equitable and irrespective of any other specified code penalty. The Referee could award a score.
To summarize, any deliberate interference with a play (usually with malicious intent) by a player or participant that is otherwise supposed to be outside of the 22 football players (11 a side) currently on the field and eligible for the play.
There have allegedly been multiple examples of this sort of specific scenario throughout history of football (which would make sense as to why it's in the rulebook in the first place), some of them true and others whose validity is questionable at best. One of the more-recent incidents and stories seems to point out a trainer at Virginia Tech University in the mid-90's who tried to trip up an opposing player during a game but failed to do so. Again, one cannot seem to track down any records to confirm this report though.
Probably the best-known true example of the Palpably Unfair Play rule occurred during the 1954 Cotton Bowl when the University of Alabama's Tommy Lewis came off the sidelines to trip up Rice University running back Dicky Maegle, who otherwise would have continued running for a touchdown. The game officials then met and awarded Maegle with a touchdown due to the interference.
However, the scenario so very rarely comes up most fans aren't aware of the rule and the possible scenario isn't even considered. Thus the Palpably Unfair Play Rule has faded into obscurity (much the like the fact that a Drop Kick is still allowed under NFL rules, even though it's a relic of when the sport was more like rugby).
For a good piece of trivia some time, ask a football fan to name all the ways in which points can be scored during an American football game. The correct answer is: Touchdown, Field Goal, Extra Point, Two-Point Conversion, Safety... and our Palpably Unfair Play/Act rule.