Underfoot

You use your small size against larger foes.

Scurry, Acrobatics 10 ranks, racial bonus to Dexterity, size Small

As a move action, you can try to slip into the space of an adjacent foe larger than you are. To do so, attempt an Acrobatics check (DC = 15 + 1-1/2 × opponent’s CR). If you succeed, you enter your opponent’s space. If you fail, you remain in your starting position, and you are flat-footed and off-target until the end of your next turn.

While you occupy a foe’s space, that foe is flat-footed and off-target. If your opponent tries to move out of your space, it provokes an attack of opportunity from you.