When Stefan grabs Matt by the collar at the Halloween party, Matt's costume stethoscope disappears and reappears between shots.
When in the Salvatore house Vicki says that she needs to go to the bathroom and then asks where it is. However, just a few minutes prior it is stated that she had been there for days so it is highly unlikely that she would be there for such a long time without knowing where the bathroom is.
When Damon and Stefan go to get Vicki from Tyler, Damon compels him to forget what happened. When in fact all supernaturals cannot be compelled unless it is from an Original.