When the Green Arrow is shot at the beginning of the episode, a revolver is used. When Oliver watches the video of the shooting later in the episode, the gunman is shown holding a semi-automatic pistol.
When The Green Arrow get shot, the leather goes outwards, like an exit wound, when in reality it should have just created a hole through the leather without moving the leather outwards.
In Oliver Queen's Metropolis loft Lois is injured by Green Arrow as he throws her across the room crashing through a glass desk. Lois calls 911 and requests an ambulance. The next scene shows her in a hospital bed at the Smallville Medical Center, which is surprising because surely she would have been taken to a Metropolis hospital. There is no mention of how she gets from Metropolis to Smallville.
Chloe is happily sitting next to Lionel Luthor at the dinner table, despite the fact that he tried to kill her and her father in "Covenant", and later sent an assassin after her. The changed nature of their relationship is considered a plot-hole which is never addressed in the show. However, this may be a result of the protection Lionel tried to offer Chloe on Dark Thursday and how both Lionel and Chloe have worked together to help Clark in the recent year.
Jimmy tells Chloe he is spending Thanksgiving at his mother's house though he reveals two years later in "Committed" that his mother left when he was young and hasn't seen her since.