When Klaus attacks Elena's house in an attempt to get in, Bonnie is still wearing her dress and elaborate hairstyle from the night before. Then, just minutes later, when she comes onto the porch to tell them that she has an idea to stop Alaric, she is wearing a shirt with red trim and her hair is long and straight. There would have been very little time between Klaus's attack and the conversation on the porch for her to change AND straighten her hair.
When Damon, Stefan, Bonnie and Klaus are talking on the Gilbert house porch, the position of the white broken fence picket on Damon's shoulder changes multiple times between shots.
S3/E21 Abby Bennett, a vampire, is let into the Salvatore house without being invited in by it's owner, Elena.
When Damon brings Bonnie to the Gilbert house, two puncture wounds are visible on her neck from where Alaric bit her. She is later seen holding a towel to her neck, presumably to absorb the blood coming from her wounds. However, she mentions that Damon had given her some of his blood to save her life, so her wounds should have healed.