Unwinnable by Mistake/Video Games/Super Mario Bros.

Super Mario Bros.

 * A glitch in Super Mario Bros 3 can cause the game to be unwinnable. In World 5, it is possible for the airship to land on the land-based portion of the map, displayed in miniature in the upper left corner of the sky map. When you then chase it down to ground level, it's nowhere to be found.
 * If you're really unlucky, then you can trigger an N-spade to appear on top of a hammer bros, causing this to happen.
 * An example thankfully restricted to one level - in World 7, one level has a Hammer Bros. Suit in it (other than this one, they're only available as world map items found in mushroom houses). If Mario is in statue form from the Tanooki Suit when he grabs it, he becomes a greyscale version of the usual Hammer Bros. Suit that can't use the pipe needed to continue the level. Fortunately, this only makes it impossible to clear that level on that life. This was corrected in the SNES and GBA remakes.
 * One fortress requires you to obtain a Tanooki Suit (if you aren't already Raccoon Mario) from a secret room accessed by P-Switch. If you trigger the switch but for some reason let it time out before you reach the bottom of the room, it's Lost Forever and you can't beat the level on that life. A similar situation can happen at the end of the World 8 fortress, where the boss door is triggered by the switch. In cases of really bad timing, you can get entombed in the blocks until time runs out.
 * In Super Mario Bros.: The Lost Levels:
 * If you go to an underground bonus room in World 3-1, you'll come out of a pipe below some blocks that you must break to continue. Since only Super or Fire Mario (or Luigi) can break blocks, there's a hidden block with a power-up. However, if you pick up the power-up and then get hurt by the nearby Piranha Plant, you won't be able to get out.
 * C-3 and D-2 both have massive jumps that can be cleared only when Mario jumps on a springboard. Sometimes, these springboards fail to spawn due to sprite limits.
 * Also happens in the original SMB. If you jump into where the springboard would be, you get stuck until the timer runs out.
 * In the American version of Super Mario Bros. 2, one could make the game unwinnable by crouching (works with the small characters as well, IIRC) and sliding into a passage of only one block height. Since the player can't auto-slide out like in the rest of the games, the character gets stuck permanently; since there's no time limit, the only solution is to reset the game and start again.
 * Not quite, at least in the Super NES version. If you resume ducking and attempt to repeatedly jump left or right, your character will eventually move out from under the block.
 * In the PRG 0 version of the cartridge, if you get hit by one of Fryguy's pieces while throwing a mushroom block at another, that piece will be thrown off the screen rather than disappear, and the game will register it as still alive, so the exit door fails to appear. The only way out is to reset or use the suicide code (Up+A+B on the pause screen).
 * For the players with OCD who must dig out every block of dirt in the pyramid levels can get themselves trapped in the left side of world 2-2.
 * The Minus World in the first game.