According to How Long to Beat, an average run of the original Legend of Zelda can take you up to nine and a half hours if you’re playing the story mode, while a rushed one would take just over the six hour mark.
However, a new record has been set by Darkwing_Duck_sda, who has managed to go through the game in just 30 minutes and 29 seconds!
The original Legends of Zelda on NES is actually exploitable, which is why Darkwing and other players have managed to finish it in such speed. According to the Speed Demos Archive, there is a glitch in the game that can be abused to clip through a wall, which Darkwing Duck uses in his playthrough above.
Here’s the technical description according to the website:
To clip through a wall (screen scroll glitch), you must stand toward that wall and be a specific amount of pixels away from the wall (either 5 or 7, the amount escapes me at the moment) and then move one frame in a side direction. This will cause Link to turn around, but stay on the same pixel. Then you can move through the wall. You only get to move through a half step of solid wall, but that’s enough to clip through things that are set diagonally, or push you through the screen transition “wall.” Clipping through the edge of the screen sends you to the other side.
If you have your own speed-run of Legend of Zelda on NES, feel free to share it with everyone by commenting about it below.