Sidekicks are a feature first introduced in Disney Infinity 2.0. They help players defeat enemies, find treasures, and trigger actions using Creativi-Toys like the Brave Sidekick Tree Door. They can be equipped with Sidekick Gear to aid in combat, most of which is unlocked randomly during gameplay.
In Disney Infinity 3.0, 107 new Sidekicks were introduced, and the ones available in Disney Infinity 2.0 were repurposed as "Disney Infinity Townspeople". They can be unlocked in the player's INterior, the Sidekick Portal (by completing portal missions), the Toy Box Hub (via Surprise Gifts), the Toy Box Takeover Toy Box Expansion Game, and the Star Wars: Twilight of the Republic Play Set. Sidekick abilities were also expanded to assist with Farming and Customization. The Body Armor items were removed, and Helmets were renamed to Hats - some of which aid in combat, while others aid in Farming, along with farming tools.
Note: While some Builders, Costumes, Sidekicks, and Townspeople may look the same, they are in fact separate Toys that each serve a different purpose.