A bucket of coal was created during the 2008 Easter event by using an empty bucket on the pile of coal in the Easter Bunny's warren. The coal was used to fuel the egg incubator and, hence, hatch a chocatrice egg. The incubator required twelve buckets of coal to be fully powered.
The bucket of coal could not have been taken outside, and players were not allowed to teleport while inside the warren. If a player stayed inside the warren with a bucket of coal in their inventory and waited until the event was over, they would appear outside, without a bucket of coal.