Let the uncontrolled chaos begin! The Double Cherry is a powerup that creates a clone of the character who uses it. The powerup stacks, so you can have several clones of a character, which will powerup when the original does. They also follow the movements of the original, but with some maneuvering, you can split them up and rejoin them. Beat the Galoombas and walk up the path. To the right is an item block with a Fire Flower. This or a Super Bell can be very helpful here. Destroy the crates near the clear pipe for another Double Cherry and the first Green Star, which is in the far right corner. Go through the clear pipe, then through the green pipe.
This drops you into an area with soldiers marching in formation. You can break their formation by defeating one of their soldiers. They'll initially panic and scatter, then combine to attack from all sides. Defeat them quickly. Make sure you have at least two characters (clones or otherwise), so you can hit the two P-Switches ahead. This will make the second Green Star appear. Take the pipe on the far right to the midpoint.
Here, you'll find more soldiers marching around on different levels, one carrying a Double Cherry. You can split up characters and easily defeat them from a distance with the Fire Flower. Grab the Double Cherry, as well as the Double Cherries from the item blocks to the left and right. Have one character or clone stand on the corner item block in the left set of item blocks. Have another character stand below and hit the item block. This will make more blocks appear, and push the character near the stamp. Ahead is a Red Coin Ring and a Fire Bro. The Fire Bro is surrounded by many clear pipes you and your fireballs can use. Once you defeat it, a green pipe will appear.
The pipe takes you to the flag. There's an invisible block with one last Double Cherry. If you have four characters or clones, have them stand on the platform marked with a 4. This will raise everyone on the platform to the third Green Star. Head for the flagpole. You get extra points for every surviving clone.
The stamp is of Fire Peach.