Character mistake: When David encourages the gang to dance at Scott's birthday party, David mistakenly calls Kelly by her actress' name, Jennie Garth. He says, "Scott, you're off, Buddy. Jen, kind of getting into it."
Character mistake: When he arrives at his hotel room in Vegas, David is surprised that Ray is performing at one of the casinos. But at the beginning of the episode, Steve told Brandon that Ray was performing, which suggests going to see him was part of their plans. So either (1) Steve shouldn't have known Ray was performing there, or (2) David shouldn't have been so surprised.
Stand (Up) and Deliver - S1-E17
Character mistake: In one scene Brenda refers to Brandon's political opponent as "Michael Miller" but a few scenes later David refers to the same guy as "Robert." He's referred to as Robert for the remainder of the episode.