Sours are characters in the Viva Pinata games and TV series.
They are grumpy characters that get their kicks from making other (usually cheerful) piñatas gloomy like them. A sour piñata is recognizable because of the fact that it'll be deep red and black in color. There are several different sour species. Each has their own bad habit, such as starting fights or scaring off other residents.
A player can tame a sour pinata by meeting its Resident requirements. Once tamed, a totem block is added to a Tower of Sour to scare away all sour pinatas of that particular species.
To tame a sour pinata, the player must first let it run its course in the garden. It will spew up sour candies, pick fights, or eat one of the other pinatas. Once it has done that it should perform the task required for residency. Once a Tower of Sour block is added, only non-sour pinata of that species will visit the garden. To attract sour pinata, the Tower of Sour block must be disabled from the menu.