From WiKirby, your independent source of Kirby knowledge.
Purple Plants is the first stage in Revenge of the King in Kirby Super Star Ultra. It can be considered to be a tougher version of Green Greens from Spring Breeze, bearing a similar topography, the same theme music, a similar opening cutscene, and a similar boss, in the form of Whispy's Revenge. Apart from the different coloration, some other differences include tougher and different enemies, and a generally expanded topography.
The opening cutscene shows Kirby chasing an orange butterfly off-screen. He briefly rolls back on screen while three Croucars and two Koozers chase him back off screen to the left.
Kirby traveling through Purple Plants
The stage begins on the purple grassy plains, though these 'plains' are rather more hilly. Kirby gets his first look at some of the new enemies on this hill, including Koozer and Perot.
In the next area, Kirby has to descend a hollow tree trunk containing Poison Mashes and Sword Knights, among other foes.
The next door leads out into the open fields, in an area that has a similar topography to the beginning of Green Greens. A side-chamber can be accessed here, but it is full of Spikes and Roselies. A Warp Star can be reached at the end of the path.
Once Kirby lands in the woods, he is ambushed by the Mid-Boss Phan Phan. The path continues to the right past several enemies until reaching the tree.
Inside the tree, the path continues upward. At the top, the door leads to the encounter with the boss (details in section below).
Enemies, mid-boss, and boss
Boss: Whispy's Revenge
Kirby attacks Whispy Woods with the Poisoned Apples.
To reach his target, Kirby must first descend via the usual route. At the bottom, he will find the old tree, this time his leaves stained purple and his bark a sickly brown. The fight progresses as usual, though Whispy's Revenge has a few new tricks. Some of his apples are poisoned, meaning that Kirby should not try to inhale them. The old tree may also drop Gordos or purple bugs from his canopy. He also can become angry and spit three tornadoes.
Defeating Whispy's Revenge yields a Sparkling Star, and allows Kirby to progress to the next level, Illusion Islands.