Acorn Plains
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Acorn Plains is the grassy first world of New Super Mario Bros. U. It lies south of Layer Cake Desert, west to Sparkling Waters, Soda Jungle and Rock-Candy Mines, and south-west of Frosted Glacier, Meringue Clouds and Peach's Castle. It is a plains world with acorn trees, shrubs, jagged mountains reminiscent of some of the backgrounds in Super Mario World and the world's most defining feature, the Acorn Tree. This special tree is one of main sources of the game's new power-up, the Super Acorn. It can be found in the game's intro, Acorn Plains' map section and said world's first level. This world has eight levels, with 5 normal levels, a secret level, a Tower level and a Castle level, a red and green Toad House, a Piranha Plant Enemy Course, and a spot where a magenta Baby Yoshi walks near. The Castle boss of this world is Lemmy Koopa.
Levels
| Level Number | Level Name | Preview | Description |
|---|---|---|---|
| Acorn Plains-1 | Acorn Plains Way | 
|
A simple grassy level that introduces the Super Acorns and the Waddlewings. |
| Acorn Plains-2 | Tilted Tunnel | File:Nsmbu underground.png | An underground level with tilted pipes and moving crystals. |
| Acorn Plains-File:Fort Icon.png | Crushing-Cogs Tower | File:World1-TowerStarCoin2.jpg | The first Tower course of the game. |
| Acorn Plains-3 | Yoshi Hill | 
|
It introduces Green Yoshi and Monty Moles. |
| Acorn Plains-4 | Mushroom Heights | File:NSMBUM&LMagentaYoshi.jpg | It is an athletic level and it introduces Balloon Baby Yoshi. |
| Acorn Plains-5 | Rise of the Piranha Plants | File:World1-5StarCoin3.jpg | Features slanted grounds and Super Piranha Plants. |
Acorn Plains- Castle
|
Lemmy's Swingback Castle | File:Lemmy's Swingback Castle.PNG | A castle flooded with lava and swinging platforms held by chains. |
Acorn Plains-
|
Blooper's Secret Lair | 
|
A secret underwater level which introduces Bloopers. |
Challenge Mode Original Courses
- Acorn Plains Speed Run - Time Attack
- Castle Coin Bypass - Coin Collection
- Full Speed Ahead - Time Attack (Original Course)
- Graceful Glide - Special (Original Course)
- Hot-Air Yoshi Ride - Coin Collection (Original Course)
- Paratroopa Panic - 1-Up Rally (Original Course)
- Star Connection - 1-Up Rally (Original Course)
- Stingy Big Piranha Plants - Coin Collection
- The Goombrat Stomp - 1-Up Rally
- Time Attack Trial - Time Attack (Original Course)
- Triple-Jump for Coins - Coin Collection (Original Course)
- Waddlewing Wipeout - Coin Collection
Boost Rush Courses
- Acorn Plains Way – Easy Pack
- Mushroom Heights – Acrobat Pack
- Lemmy's Swingback Castle – Flying Squirrel Pack
- Yoshi Hill – Yoshi Pack
Trivia
- In early builds of New Super Mario Bros. U, the Acorn Plains map looks substantially different. The map was significantly less detailed, the Acorn Trees did not show the Super Acorns, the map had two red Toad Houses, and the green Toad House was in a different spot, there are two Enemy Courses instead of one, a secret exit was planned to appear in Yoshi Hill which revealed a bridge to Lemmy's Swingback Castle and the spot where the Balloon Baby Yoshi was, is gone.
- Previous footage of the Acorn Plains map have depicted the pipe that the Piranha Plant is nesting in as green, instead of red.
