Michael crashes into Lelaina's car on the left-hand side. After she visits him at his office, she is shown getting out of her car with Vickie at their apartment - yet the car is in perfect condition without any dents.
When Vickie is writing in her notebook, she writes the date as being September 26. A few scenes later, Lelaina is speaking with Michael in his office and his computer has the date as being September 21.
The camera angle changes in the final camcorder shot of Lelaina saying "...and you wondered why we never got involved."
When Vicki and Lelaina return to their apartment after the car accident, when she's walking up the steps Janeane Garofalo has sweat patches under her arm; when she gets inside they have disappeared.
Troy's hair in different shots while talking to Michael outside of the club.
At one point, the characters are drinking Big Gulps from 7-Eleven. This would have been impossible in Houston in the early 1990s. All Houston-area 7-Elevens (269 total) were acquired by National Convenience Stores (parent company of Stop'n'Go) in October 1987, which was later consolidated by Diamond Shamrock (National Convenience Stores and Diamond Shamrock entered into a buyout agreement in November 1995). Valero Energy Corporation now owns the assets of Diamond Shamrock since 2001. To get a Big Gulp (prior to September 2013), they would have had to drive 109 miles to Smithville, Texas - the easternmost location of a 7-Eleven in the state east of Interstate 35. 7-Eleven Inc. owned/operated stores including those corporate-owned in Texas, prior to December 31, 2012 were limited to Austin and Dallas-Fort Worth metro areas along the Interstate 35 corridor - its West Texas stores are operated under license by Alon USA's Southwest Convenience Stores retail division. As of January 2, 2013, 7-Eleven acquired the retail assets of the C.L. Thomas Petroleum Carriers and TETCO where the existing Speedy Stop and TETCO stores are being remodeled as 7-Elevens, officially reintroducing the brand to Southeast Texas - with several locations in the outlying area of the Houston Metro region. As of early 2014, the closest 7-Eleven to the Houston, TX metro area is located in Edna, TX off U.S. 59.
When Troy is singing "I'm Nothing" in the club, his strumming does not match the sound of the acoustic guitar.
When Lelaina leaves the club where Troy is playing with his band, when he and Michael run out after her, we see her BMW driving away, however if you freeze-frame, the driver is clearly a man.
When Lelaina totals all of the money she 'earned' from the gas station in her notebook, she sums the amounts as $389.84, when the actual total is $393.97.
The opening has Lelaina Pierce graduate as valedictorian of her college. Yet throughout the film she comes across as immature, irresponsible, and not particularly bright. When pressed she can't even define irony.