World 5 (Super Mario Bros.)

World 5 is the fifth world of Super Mario Bros.. World 5 introduces a new enemy, the Bullet Bill, along with the Bill Blaster. This world features shorter time limits and harder levels. Levels, though, start to repeat from this world on, only with increased difficulty.

Trivia

 * At the start of World 5-1, a fortress is seen instead of a castle. This wasn't changed in Super Mario All-Stars.

Mondo 5 (Super Mario Bros.)