Continuity mistake: When Lloyd calls Diane's house for the first time to ask her out, he gives her father his phone number as 555-1342 (several times), but later when Diane is reading her list of messages, Lloyd's number is listed as 555-2342. (00:12:40 - 00:15:50)
Continuity mistake: Right after Lloyd gets his nose broken while kickboxing, Diane begs him to take her back. As they converse, the string of drying blood under Lloyd's nose changes from being to the right of his nostril to directly under it.
Continuity mistake: When Lloyd and Diane are driving during the scene where Diane breaks up with him, Lloyd is continuously looking at Diane for very long periods of time without looking back at the road. It is very obvious, and surely he would have hit something eventually. (01:02:05)