The narrator plays a big role in "The Knight's Tale," constantly making his presence felt. He doesn't do this in the same way as most of Chaucer's narrators. Unlike the Man of Law, for example, he doesn't give an emotional reaction to the story. Instead, he makes his presence felt by reminding us that he's the one telling this story, that he's in charge. Describing (or rather, failing to describe) Theseus's homecoming, he justifies his omission with "al the thyng I moot now forbere / […] / the remenant of the Tale is long ynough" (27-30). He's saying that he doesn't want to talk about Theseus's homecoming because he's got enough to tell us without that.
The narrator does this all the time. You probably noticed how he constantly justifies leaving out particular portions of his story because the tale is already long enough. He also can't help but tell us about the things he's leaving out. You know, the good ol' "I won't tell you about how I lost my tooth in a fight, or about how vicious the fight was, or about how my mom grounded me afterwards." But wait. You just did tell us about that. Oh well. The narrator also signals movement from one subject to another with "and now I leave X and turn to Y."
Really, there's rarely a moment when we're not aware that we're in the hands of a narrator. The impression this creates is of a strong, confident storyteller who, kind of like Theseus's God, has a plan for his tale.