Error

Error is a citizen of the town of Ruto in the Zelda II: The Adventure of Link. A rather infamous NPC, he is found inside of a house, which usually denotes that the occupant has something vital to tell Link, but he merely repeats his single line of "I AM ERROR" until the player meets a second man in Mido Town, at which point an attempt to converse with Error will provide the player with information on how to find the passage to the third palace.

Error's single, seemingly unhelpful line was met with confusion and amusement from many players, giving him almost legendary status in fandom.

It is likely that the name Error is a joke from the developers, since he is close friends and quest-related to the character Bagu. "Bagu" would be the romanization of the Japanese way of writing the word "bug". As such, "error" and "bug" refer to a computer's malfunctioning.

Another possible origin for the name would be the fact that the Japanease lack an L in their language, so the message might have meant to have been "I am errol"

Trivia
In the Wii video game, Super Paper Mario, one of the first bosses of the game is a robotic dragon who is attacked by an evil character, Dimentio. Upon being attacked, the dragon malfunctions and begins to say several incoherent phrases, one of which is "I AM ERROR".