[Tomcat68]

You cannot have any type of extra men in the huddle for deception. If a player comes into the lineup one must come out and be off the playing field. You can,however, run a player off the field and put a player in the game on the sideline as long as they are 3-4 yards, i believe, on the field. Some coaches use this as a trick type of play.

The bolded area is false. Teams will do this because officials will very rarely make the penalty call. Any player entering the game must atleast reach the numbers that run along each sideline to be officially checked into the game. They can then retreat back towards their own sideline, but they must reach the numbers first.