Companions
Companions are small creatures who follow the player around. They have no function and provide no benefit, aside from following the player.
To enable/disable companions select 'Companions' inside the 'Wardrobe' option in the inventory menu.
Collecting Companions
Some companions will be available as special promotions - either through events or as rewards for limited events.
Every unique small animal in the world can also be collected as a companion. To befriend a critter as a companion first give it its favorite food. This will register it in the Collection. Once registered, feed that critter type twice more to have it join the player as a companion.
Since each critter can only be fed once every 24 hour period, recruitment will take multiple real world days.