Ninja Pigs are a group of pigs that can swap places with other pigs when in danger.
Ninja Pig's ability is utterly useless, as he has the same strength with other pigs and swapping places with other pigs will make no actual diffrence to the level. (unless swapped with flying pigs) Pop as you would with regular pigs.
Ninja Pigs' can not only swap with regular pigs, but also pigs with abilities.
Ninja Pigs are also appeared in Angry Birds Epic but have different abilities and names (Black Ninja, Red Ninja, and Ninja Bowman).