When they steal the bus from the school for the blind, it never has plates on it. After they arrive in Austin, plates somehow show up on the bus but then disappear and reappear for the rest of the movie.
When Rubin is trying to convince Kyle to let them jump the bridge, he says that the car weighs 1600 lbs, and with the humans and cargo it weighs 2100 lbs. However, 4 adult males would weigh more than 125 pounds each. And that does not count the weight of their belongings.
When Josh proposes a monetary bet to E.L. over whether or not he slept with Beth, E.L. refuses, stating that he wouldn't bet money on something Josh couldn't prove. Logically, if this were the case, it would work in E.L.'s favor, since Josh's claim couldn't be substantiated.
Right after the scene with Kyle and Rhonda, they all get on the bus heading to the clinic to donate sperm. Right before that, they all ask Kyle how it went with Rhonda and he pulls out her underwear. E.L. says "did you kill a cheetah?", but it is actually leopard print.
In the beginning of movie Josh puts 3 stamps on the envelope to Tiffany. When he gets the mail back in Austin it has 8 stamps. While his friends could have added them when they went to the post office, it's unlikely that they managed to also move the stamps closer together and change both the address and return address, which are completely different.
At the end of the movie, Kyle's Dad points a gun at several people, then when Kyle stands up to him, he throws a punch with one hand and the other hand is clearly visible and not holding the gun anymore.
When the four boys are driving down the road in Kyle's car, there is no space in the front car bumper for a license plate. But before they jump the bridge there is a gap in the bumper where a license plate has been removed.
When in the frat house during the step routine, one of the guys watching is wearing a yellow long-sleeved Polo shirt. The film has been reversed in this scene, as evidenced by the pony emblem being on the wrong side of his chest and the emblem itself appearing reversed.
When Barry is seen plucking the string at the front, his hand is near the hole in the center of guitar body. When he's seen at the side, his hand plucking the string is much lower on the finger board (guitar neck)
In the bus heading to Boston, Beth is holding the cup with its handle in her right hand. Then in the close-up the cup's handle is in her left hand with the forefinger through it, then again in the right hand.
When Rubin comes up to the motel clerk (to buy marijuana), the phone is ringing. In the close-up we see the phone on the blue part of the counter. In the rest of the shots it is on the part of some kind of beige or sandy colour.
In the beginning of the movie (while the credits are still rolling) while Barry is giving the tour of Ithaca University, the father of the African American prospective student is played by two different extras. In one scene he's an older man with gray hair. Then, as the tour continues, he briefly becomes a younger man whose hair appears to be dyed. Then in the following scene he's back to being the older guy. He even has a speaking part "That's probably because he's never been anywhere else."
When Josh hooks up with Beth, she interviews him for the video and asks him what he looks for in a girl. He says, "Topless and topless," but later in the film we see part of that video and Josh only says topless once.
In Josh's dream sequence in which Tiffany and her friends watch the sex tape, the contents of the video can be seen in the mirror over the girls' heads. Beth can be seen taking her top off in the video, but then a moments later she is seen taking her top off again when the camera switches to the actual TV screen.
Near the beginning of their trip from New York to Texas, they enter a tunnel on the Pennsylvania Turnpike, and the very next shot says that they are crossing the New York state border into Pennsylvania.
When Josh tries to call Tiffany after having the bad dream he only pushes 7 digits as if making a local call when she supposedly is in Austin, Texas. He should have pushed 11 digits to place the long distance call.
When they load up Kyle's Taurus for the road trip, it has a West Virginia license plate. Later, the film shows Kyle's parents eating at a restaurant in "Upstate New York", which they've been going to "every day for twenty years". However, this statement is proven to be wrong/a joke, so the license plate is not necessarily inconsistent.
When Josh leaves his Philosophy class he finds out that he needs a B+ on his midterm to pass the class. When they walk outside there are bright green leaves on the trees. This is consistent with midterms in early October, which is consistent with, e.g., Cornell's academic calendar.
While they are in the diner waiting for new french toast, the waiter comes over to refill the coffee. While he is talking to them, he puts his hand on the bottom (metal section) of the pot of supposedly "hot" coffee.
When Tiffany starts watching Josh's video, we see that it's
different from that which was made at the beginning of the movie. This one leaves out such phrases as, (Beth) "Do you feel better yet?" (Josh) "I feel a little bit better, yeah..." Besides it zooms at the moment Beth was taking off her skirt so she couldn't do that herself.