New Super Mario Bros.: 2-Castle

This is one of two special castles. First, we have to deal with spike balls, which can destroy all types of blocks. We can dodge them in alcoves above and below their path. There is a path that goes up to the first Star Coin. Wait until the spike ball passes, then wall jump up, then duck into the alcove to get it. There's a door to the outside at the end, but there's a spike ball before you reach it. Outside, you'll find lots of Bullet Bills. Bounce off of one to reach the second Star Coin past the blocks. We hit a switch to progress and dodge a spike ball. We go over the large spike ball with a rope and land on a ledge with a Mini Shroom which allows us to progress. We need to be Mini Mario to reach the third Star Coin. We can get a Super Shroom or stay small. A switch reveals the boss door. Go through it quickly to avoid the spike ball. We fall into a pit with the mummy Pokey. To defeat it, we can stomp on it as regular Mario or ground pound as Mini Mario. Three hits will kill it. After we get the key, the wall lifts up to reveal Bowser Jr. and Peach, who run off. This is where the path splits. If we're not small, we'll go to World 3. If we're Mini Mario, we'll fall through a tiny gap and the sign will flip and say World 4. We'll go to World 3 first.