Plumbers, upon birth, are granted the great fortune of being able to die twice and still continue their existence. It doesn’t matter how, either. Fall down a pit? Second chance. Hit by a bullet? No problem. Run out of an arbitrary amount of time presumably set by the Koopa Gods? Just wind back the clock. Of course, it’s likely those things will happen to plumbers more than just three times during the span of their careers. They can earn more chances to fuck up. Why, the St. Peter of plumbers takes 100 gold coins in exchange for a second life. He also takes poisonous mushrooms.
But the most obvious way Mario and Luigi can become immortal is by jumping on animals without touching the ground. Not just a couple of times, though, like most humans are used to. Step on a turtle or a beetle nine times without hitting land is a feat blessed by the Heavens. There’s only a few places one can accomplish this, the most famous being the stairs at the end of 3-1. The rhythm is difficult to master, but if you nail a turtle just right, you can keep stomping on his diamond-hard shell as long as you want until time runs out. Once you die, you may find yourself with nine lives, or square lives, or even what the hell kind of shape is that lives (hint: it’s a lot). Be careful, though. The Gods frown upon Mario approaching true immortality; get too many lives and you will die permanently.