Revealing mistake: When they arrive at the University, they drive through a puddle and stop. On the road you can see wet marks for previous takes. It's clear it's from the previous takes as the marks stop exactly where the bus stops. (01:12:50)
Factual error: The first time it shows Josh calling Tiffany he only pushes seven numbers. A call from N.Y. to TX would require 1-(area code)- then seven numbers = 11 digits.
Continuity mistake: In the first scene of the movie where you see a bird view of the city you can see the filming helicopter on the bottom right corner of the screen.
Continuity mistake: When the guys arrive at the University of Austin, Kyle has a cigarette behind his right ear as they get out of the minibus and as they start their walk. The cigarette has disappeared in the next shot (when Kyle trips over himself).
Continuity mistake: During one of the driving scenes along a motorway, they are driving up the right hand side of the motorway. On the other side, traffic is coming towards the camera (as it should) but there is a broken down vehicle that for some reason is facing the wrong way, as if someone reversed down the motorway and broke down.
Continuity mistake: The diner they have breakfast at is the Gwinnett Diner (located Northeast of Atlanta), this can clearly be seen on all the coffee mugs in the kitchen. Many of the signs along the highways were either blurred or digitally altered to go along with the story.
Answer: It's funnier if Jacob constantly bothers the characters and gets away with it, and receives his comeuppance in the end in an over the top manner (he forms a suicide cult but is the only member that actually kills himself).
BaconIsMyBFF