Niko is a character who appears in The Legend of Zelda: Wind Waker, The Legend of Zelda: Phantom Hourglass, and The Legend of Zelda: Spirit Tracks, though he appears more prominently in the first and third games. In Wind Waker, Niko is part of Tetra's pirate crew, and is the lowest ranking member (except during the short interval that Link is part of the crew). Niko gives Link puzzles to solve, the first being on the way to the Forsaken Fortress, the next time being when the ship is docked at Windfall Island, and gives out certain important prizes each time. He again appears in Phantom Hourglass, though much like the rest of the crew, he only appears for a short time, whenever the crew happens to be shown. In Spirit Tracks, however, he was given a semi prominent role, being the only surviving person from the previous games, as the rest have passed away. He tells Link stories and gives Link a side quest to do as he travels: collect stamps for a stamp book. As Link collects stamps, he will give Link rewards. He also notes how much the current Link looks like his predecessor (for good reason).
Niko may not be very coordinated, as he expected Link to take much longer on the tests (i.e. He thought Link would take a year to complete the first test), which may be how long it originally took him. He hadn't even done the second test himself.