Firecrackers undergo 3 stages until they explode. They will randomly destroy (actually collect) cropsies and thus also stir up an otherwise stuck board. You need to accomplish a match to advance a Firecracker. As usual you can advance more than one at a time. Levels with Firecrackers tend to be lucky but they are rarely stuck. Igniting a certain amount of Firecrackers is a goal in some levels.
Level
Firecrackers first appear in Level 356.