Barrel of Monkeys

The Barrel of Monkeys are a real-life toy by Milton Bradley seen in the Toy Story series. Andy Davis owns a yellow barrel of them.

Toy Story
They were used by Rex as the toys try to save Buzz Lightyear after falling out of the window of Andy's room in Toy Story.

Toy Story 2
They later appeared in Toy Story 2 where Andy has Hamm as "the Evil Dr. Porkchop" giving Woody the choice of "shark" or "death by monkeys" for Bo Peep. Later, they appear in one of the outtakes, harassing Mr. Potato Head, when Mrs. Potato Head suggests that he take monkey chow with him in his parts storage on the journey to save Woody.

Toy Story 3
They are seen in the opening of Toy Story 3 during Andy's play scenario that takes place in the wild west. Hamm, as Evil Dr. Porkchop controlling his ship, activates the button labeled "Death by Monkeys," which unleashes a barrel that explodes when it hits the ground, sending thousands of monkeys scattering in all directions. The monkeys grab Woody, Jessie, and Buzz, holding them hostage, as Mr. Potato Head, whom Andy portrays as the villainous One-Eyed Bart, prepares to finish them off. Later, when Woody gathers all the toys remaining, none of the monkeys are seen.

Trivia

 * Aliens hanging in the same fashion as the Barrel of Monkeys appear in Buzz Lightyear's Laser Blast.