Marmosets

Marmosets are small monkeys who are the "minions" of Nigel, sent to defeat the Birds after they escape from Smuggler's Den. These Marmosets act in the role of antagonists, as the Bad Piggies do in the Classic Angry Birds game. Unlike Pigs, Marmosets can roll back right-side-up after being tipped over. They occasionally survive after falling. Their hitboxes are also rectangular, as opposed to the pigs’ round “hit balls”

Marmosets do not take damage when bounced onto floaties or parasols. In the final level of Carnival Upheaval, the head of the marmoset, Mauro, appears as a boss.

Trivia

 * Marmosets appear in the Rio 2 levels, but in the movie, they are absent.
 * In the game, Marmosets make Chimpanzee sounds, but in real-life, they chirp.