World 1 (Paper Mario: The Thousand-Year Door)

World 1 is a level in Paper Mario: The Thousand-Year Door, played during the Bowser intermission following Chapter 2: The Great Boggly Tree. Its name is denoted as World 1-X, with X being the number of attempts that Bowser has used for the level. Like other Bowser levels, Bowser has unlimited lives. The music that plays during this level is an arrangement of the "Ground Theme" from Super Mario Bros.

Story
After Bowser and Kammy Koopa arrive in Petal Meadows looking for Princess Peach, Kammy tells Bowser that Peach was spotted in Petalburg, so Bowser enters World 1 to travel there. Once in Petalburg, Bowser confronts what he thinks is Peach standing by a window, but a Koopa Troopa reveals that it is actually his life-size Peach poster, which disappoints Bowser.

Layout
This level is a side-scrolling platformer level starring Bowser, in the style of Super Mario Bros. Its layout is similar to World 1-1 from that game. The level starts with a Goomba, which runs away from Bowser if he approaches it, and several Brick Blocks which Bowser can break four at a time if he hits them from below. A yellow block is also present, which behaves like a ? Block; if Bowser hits it, the block is destroyed and Meat appears. If Bowser touches the Meat, he grows larger and can take an extra hit, similar to the effects of a Super Mushroom. Following this section are two Warp Pipes which cannot be entered, an X-Naut which charges at Bowser, and another yellow block containing Meat. If Bowser collects two pieces of Meat without taking a hit, he grows to a gigantic size, starts flashing yellow, and becomes invincible, similar to Mega Mario. In this form, Bowser is also able to break Brick Blocks, yellow blocks, and Warp Pipes upon contact from any side. At the end of the level is a staircase made of Brick Blocks and a flagpole, both of which Bowser can destroy if he is gigantic. Reaching the flagpole completes the level and briefly displays the word "FINISH". There is also a small castle next to the flagpole, as another reference to Super Mario Bros.