From the
Moving Through a Square entry of the
Pathfinder RPG Reference Document and the
Movement, Position, and Distance section in the
Hypertext D20 SRD (for 3.5 D&D):
Quote:
Moving through a Square
Friend
You can move through a square occupied by a friendly character, unless you are charging. When you move through a square occupied by a friendly character, that character doesn’t provide you with cover.
Opponent
You can’t move through a square occupied by an opponent, unless the opponent is helpless. You can move through a square occupied by a helpless opponent without penalty. (Some creatures, particularly very large ones, may present an obstacle even when helpless. In such cases, each square you move through counts as 2 squares.)
If you want to try to sneak past the enemy linemen to sack the quarterback, you want the Overrun combat maneuver/special attack.
