Pulling a quarterback from the game, then putting him back in

[starman]

the third QB rule works this way:
On game day each team gets to activate 45 players and designate a 46th player the emergency qb. If the emergency qb enters the game before the 4th quarter, then the first two quartebacks are not elligible to play in the game agian.
A few years back there was a game between the redskins and eagles where the first two redskins quarterbacks were knocked out of the game early. However, there was a chance that one one them would be able to return to the game. If they were to use thier emergency qb, the other two quartebacks would not be able to return. Instead, they let Brian Mitchell (running back/ return man) play qb for a possession. He managed a pretty long TD drive.