Every 100th level is a dragon boss. Each clip below is rendered from the game's own dragon drawing code with the same timings the board uses. The cage size is the real one for that boss.
In the game the chains break as you clear arrows, so the caged part lasts the whole level. The clips shorten that to two seconds. The board shakes and sparks fly from the cage, and the roar sound plays. None of that is shown here.
Ashborn