The unnamed friend in My Thoughts on Mackenzie Weaver functions as the central figure, though not the point of view character, in the story. He is introduced by the equally unnamed narrator, who describes him as a strange, antisocial student at his college, known for discussing conspiracy theories like "...Stonehenge or Elvis or that airplane disaster". The friend inserts himself into the narrator's college life, introducing him to the story of Mackenzie Weaver, which the narrator becomes interested in despite himself.
The friend and the narrator discuss Mackenzie via the Internet over summer break, and one day the friend shows up at the narrator's house unannounced. They go for a drive, and the narrator all but admits he was one of Mackenzie's surviving classmates before the now-undead Mackenzie appears and runs him through with her cutlass. The narrator suffers psychological trauma from his friend's death, but no legal repercussions, as there was nothing connecting them besides attending the same college. Throughout the story, the friend appears knowledgable about all aspects of the Mackenzie conspiracy theory, other than her actual motives.