Super Mario Advance 4: Super Mario Bros. 3
Bugs/glitches

Fierier Bros.
As if the Fire Bros. weren't tough enough, this glitch can double or triple the amount of fireballs they spit at you. Pause and resume the game as they're spitting fire, and they'll spit out two more fireballs. Quickly pressing pause again to get them to add two more is not too difficult. (Fire Bros. are only found in World 2's secret area and World 8-Hand Traps.)

This does not work in the original Super Mario Bros. 3 because the Pause screen is different.
--[Found by Deezer]