Al Sah-Him - S3-E21
Character mistake: Diggle turns to Nyssa and says "I think what she's trying to say is, Oliver would never do anything to hurt you, Felicity," incorrectly addressing Nyssa as "Felicity." (00:14:50)
Death at Victoria Dock - S1-E4
Character mistake: Fisher refers to some characters as speaking "a Slavic language." The characters are Latvian anarchists. Lettish (aka Latvian) is a Baltic language, not Slavic.
Character mistake: They are in the interrogation room questioning the fiancé of the scientist Natasha when the captain says, "the blood we found at the scene of your fiance's murder, it didn't belong to Bobby Cordero." The characters name was Benny Cordero, which the captain says correctly a few lines later. (00:33:25)
Just Stuck It in That There Doo-Dad - S3-E3
Character mistake: At the start of the episode, Jimmy says he met Cookie at work. The scene then changes to the strip club where Cookie is working and Jimmy is there looking for Bobby. In the Season 1 episode "The Horny Bastard", Jimmy tells Cookie that they met when he robbed her dad's liquor store.
Caleidoscope - S2-E4
Character mistake: The chess set in Dr. Pierce's home office is set up incorrectly. When the men are set up properly, each player has a light colored square in the right-hand corner. The board as it appears in the show is set up so that the light-colored square is in each player's left-hand corner. This "beginner" mistake puts the king and queen in the wrong positions.
Character mistake: The doorman tells Ike that Jimmy Shoes and the prostitute left in a '55 Chevy, the car is a '56 Chevy.
Episode #5.3 - S5-E3
Character mistake: The chief baddie spells definitely as definately.
Suggested correction: When Diggle is walking away from Felicity, he is still talking to her but it looks like he is talking to Nyssa.
Stephen Edmonds 1
People have already tried to correct this mistake. It is valid. In the scenes prior, Nyssa says Oliver will do what it takes to kill her and Oliver says "tonight, Nyssa Al Ghul faces justice." Nyssa is there to bring the team the news that Oliver is going to try to kill her. Felicity says "Oliver wouldn't", meaning Oliver wouldn't try to kill Nyssa. Diggle says "I think what she's [she being Felicity] trying to say to say is that Oliver would never do anything to hurt you" [you being Nyssa whom Oliver is going to try to kill]. He is meant to say "Nyssa." Otherwise the entire line means Nyssa or Laurel are there to convince Felicity that Oliver would never do anything to hurt Felicity.
Bishop73