Gamers often complain about day one patches and games releasing with devastating bugs they have to avoid in order to patch. What a lot of people do not realize is that games always had these problems. The main difference is the copy one owns could not be patched, leaving them with a potentially game breaking bug for eternity.
The following NES games all had game breaking bugs players could run into. Some were fixed in later versions of the same game - which is way more inconvenient than downloading a patch - and at least one of these games put the bug in as a feature.
10 Monster Party
In the seventh level of this action platform, beat the seventh boss and collect the key. Go to the next boss - a giant spider - defeat it, and then leave the room. Return to the room and there will be no key and the boss will no longer be there. Curiously, this game never came out in Japan, so gamers in the east can consider themselves lucky they did not run into this glitch.
9 Ninja Gaiden
While the game is still technically beatable with this bug, it makes the game infinitely harder. Losing to any of the last three bosses sends the player back to the sixth act. This was initially a bug, but the developer left it in to increase the challenge. Ninja Gaiden was infamously difficult, and looking back on it reveals a brutally unfair action platformer. The 2004 reboot is a significantly better example of a game that is fair with its difficulty.
8 Zelda II: The Adventure Of Link
The second Legend of Zelda is an outlier in the franchise due to its Side-Scrolling nature. It is considered one of the weaker entries, but still has its dedicated fanbase. If you activate the fairy spell while not on the screen, it can destroy the palace without having completed it, preventing the game from being properly beaten. It is pretty difficult to do this one by accident, fortunately.
7 Metroid NSFW Password
Most games for the NES required passwords to save progress. Only a few games had actual save states, like the original Legend of Zelda. In Metroid, enter the password "Engage Ridley Mother F*****", only with the last five characters using the actual letters completing the expletive.
Doing so has several possible reactions. Sometimes the game will crash or sometimes it will send the player back to the title screen.
6 Super Mario Bros. 3 Airship Glitch
Super Mario Bros. 3 is still an incredible feat to think about. Fitting such an ambitious game on the NES did not come without some rough edges, however. If you die on the airship in world 5, there is a small chance the ship will disappear, preventing further progress. Considering it is easily one of the top three games released for the console, it is worth the risk to play this magnificent platformer.
5 Super Mario Bros. Jumping Too Hot
Pretty much every level of the original Super Mario Bros. ends with Mario mounting a flag pole and sliding down. It is possible to jump over the flag and get to the other side. Continue going right until the flag is off screen to end up in an infinite expanse of nothing. The only way out is to let the timer go up. There is nothing particularly fun here, so we do not recommend doing this glitch.
4 Stone Glitch Orange Ocean 1 Kirby's Adventure
In the Orange Ocean 1 level of Kirby's Adventutre, one of the mini bosses starts you on a breakable platform on the top left corner of the screen. Use the stone ability to break through and end up stuck in the air, floating on what appears to be water. Use the stone ability again and the game will likely crash. Pressing B and Start right after each other can cause even more glitches. One has to love the randomness of this particular glitch.
3 Super Mario Bros. 3 Hammer Bros.
The innovative map of Super Mario Bros. 3 can cause some problems prior Super Mario games did not have to worry about. For example, if the Hammer Bros. and a card matching game end up meeting each other on the world map, the former can lock into place, blocking progress.
Unfortunately, playing the SNES version packed in with Super Mario All Stars does not make you safe from this glitch.
2 Action 52
It is almost unfair to even include Action 52 on this list. The cartridge comes packed with 52 titles, but the whole thing is barely playable. It is packed to the brim with technical issues. One of the games, called Ooze, has an infamous bug which freezes the game at the third level. It is notable because a contest was held guaranteeing a cash prize for those who beat the fifth level. While perhaps a solid joke, it is not very funny when someone strapped for money is trying to make some extra cash.
1 Minus World In Super Mario Bros.
This is perhaps one of the most famous NES glitches of all. Entering Minus World requires the player to glitch through the blocks and pipe at the end of the second level. Unlike the traditional way of reaching the warp zone, the screen does not start scrolling. Go through either the pipe at the left or right and Mario will end up in the Minus World, a never ending underwater level. With no way to escape except death or resetting the console, you are doomed to an eternity of swimming.