Burger World is a planet seen only in the episode, Anti-Poof. It is a fast food restaurant located on a large floating rock in the middle of space. Foop destroyed it in his quest to become the only Fairy baby in existence.
This restaurant is essentially a fast food stop for space travelers. It was destroyed by Foop after he discovered they were giving away Poof toys in their "Peppy Meals". When Timmy called for help to stop Foop from destroying Poof, he appealed to all Burger World employees. At least one Burger World employee did show up to help. This planet is repaired when Poof was able to successfully make Foop cry (since the latter's crying causes good things to happen).
Burger World is a parody of Burger King.
The "Peppy Meals" sold at this planet are a parody of Happy Meals, a kids meal that has toys in them, which is sold at another fast food chain, McDonald's.