Never Kill A Boy On The First Date - S1-E5
Other mistake: In the famous scene where Buffy tells Giles, "If the Apocalypse comes, beep me," she grabs her pager from out of shot. Trouble is, she's standing in the middle of her hall and there's nowhere she could have picked the gadget up from. (00:21:00)
Other mistake: When T.J. types in his height instead of Floyd's while searching for his dad's date on the computer, he never pressed the "Enter" key.
Other mistake: At the start when the Lexus is found it is shown as a mirror image as can be seen by the badge and registration number. (00:03:57)
Opera House Murder Case: File 2 - S1-E22
Other mistake: In the flashback with the sulphuric acid bottle dropping on Fuyuko, the bottle has still the cap on, making the incident as it is shown impossible. It should also be noted that there's a shattered glass noise, but in the previous episode we saw the bottle was perfectly intact on the floor and was even reused for a murder (although how could the culprit be in possession of it is a mystery - it's the same one since the stain on the label is identical). (00:15:55)