Factual error: In the montage sequence showing Drew Barrymore hanging out with the math club, they have a Pi poster with 3.1457869986. Only the first 3 digits are actually correct. (Pi = 3.1415926535897...) (00:25:20)
Factual error: Also shortly after the boy is shown he walks towards Drew and goes to dump his soda in her bag. The Pepsi One can turns into a Sprite can of new design, rather than the design which would have been used at the time. (00:13:20)
Answer: Over the course of the evening, Guy learns that being popular isn't the most important thing in the world and wanted to make peace with Aldys. I think he was genuinely being a nice guy and wasn't in on the prank.