This level will be another autoscroller, as you will be on a train. As soon as the level begins, quickly get onto the train itself and snag Green Star #1 to your left. Hop back down and you can pick up a Cannon Box (not really needed), then jump back on the next car. Flopters will drop in from above, but the nearby ?-Block has power-up (Super Leaf, if big). Continue right to where the Cat Bullet Bills will seek towards you. Ahead is a Goomba Tower with Green Star #2 atop, so chop them down to size and retrieve the Green Star.
Crates are on the next car and blowing them up will reveal a Mega Mushroom, which is useful for racking up points while not taking any damage. However, if you decide to use the Mega Mushroom, you have to make sure you don’t destroy the green pipe. Enter that green pipe to find Captain Toad in a crate on the far train; freeing him rewards Green Star #3. Cross back over to the Bullet Bill Express where two Fire Bros guard the lead car, one on top and one guarding a small tunnel. Take them out and claim the Stamp from the lower portion of this car before using the pipe.
BOSS - Pom Pom
Pom Pom is a miniboss that is similar to Boom Boom, in that she will do a specific gimmick. Hers is being able to split up into multiple copies, with two being during the first round, three the second, and five during the final hit. After splitting up, Pom Pom and her clones will all throw their shurikens at you. You might think it’ll be difficult to find and hit the real Pom Pom, but the clones won’t have her green ribbon, plus the clones’ shurikens are grey in color, compared to the pink one. Using that knowledge, it’s easy enough to jump on top of the real Pom Pom. Hit Pom Pom three times to defeat her.
Enter the Warp Box that appears after Pom Pom is gone, snag the clock, then grab the top of the Goal Pole.