The Crown Rush event lets you earn items to help you at the beginning of a level!
You earn 1 Rocket and 1 Bomb at the beginning of a level after completing a level. If you complete the next level without losing, you get to start the next level with 2 Rockets and 2 Bombs. Finally, if you complete another level without losing, you will get 3 Rockets and 3 Bombs at the beginning of the levels!
When you fail to complete a level, you will need to start over to earn the items at the beginning of the level again.
You can see the crown rush event after reaching level 25. If a crown rush event is already in progress when you reach level 25, you'll need to wait for the next event to start.