B-1

B-1 can refer to the following:
 * World B-1 from Super Mario Bros.: The Lost Levels.
 * Room B-1 from Mario vs. Donkey Kong: Minis March Again!.
 * A Job for a Plumber, mission B-1 from Luigi's Mansion: Dark Moon.
 * Level B-1 from Mario vs. Donkey Kong: Tipping Stars.

B-1