This is a video of a recently discovered Super Mario Bros glitch that awards infinite 1-ups (although you can only keep 128). Wow, thirty years later and people are still discovering new tricks. Although how anybody discovered this one is beyond me. First you have to beat the game, then start a new 2-player game (like new game+) and have one player die while a vine is growing and then it will continue growing up through the ground on the next player's turn. And, if that player is on a level with two trapped enemies, you can repeatedly booty-bump them for free lives. And I thought running around in games trying to find cracks in the walls was fun!
Keep going for the how-to video. Although having to beat the game first to get infinite lives seems a little redundant.
Thanks to E V I L A R E S, who is so evil he once choked out player 2 with a NES controller cord.