The Chocolate Chicken is found in the Easter Bunny's burrow during the 2016 Easter event, and was created after the Easter Bunny added a potion to his chocolate mix. During the event the player must chase the chicken until it they are able to corner it and finish it off.
The chicken returned in the 2018 Easter event as a monster that must be defeated depending on which idol the player picked during the event. The colour also changes based on this. However, the Colossal Chocco Chicken will summon regular coloured chocolate chickens.