During a second playthrough Mario can obtain unlimited extra lives in World 1-2 through a glitch.
The player must start a 2 player game and Mario must die in World 1-2. As Luigi, the player must reach World 5-2 and die climbing the vine that comes out of a block next to a Hammer Bro.
When Mario re-starts World 1-2, the vine from World 5-2 will grow through the ground. Mario can can then climb the vine and come down between the Buzzy Beetles and earn 1-Ups.