Episode #5.3 - S5-E3
Character mistake: The chief baddie spells definitely as definately.
The Case of the Wandering Widow - S4-E6
Character mistake: As Mr. Morgan (Dean Harens) is being examined by the prosecutor he's also sitting in the gallery.
Character mistake: Nick asks Janette if she's ever turned anyone else into a vampire - an odd question, considering the fact that he already knows she has. He was there when she brought the baroness across in the 18th Century flashback sequence for "If Looks Could Kill." It's even odder that Janette tells him she's never done it, since she knows that Nick knows she has. Apparently, the only one not in the know here was the scriptwriter.
Character mistake: Nathan suggests to Dwight and Audrey that maybe he should shut down the meeting of troubled people. As chief, he should know he has no authority to stop citizens from assembling.
Character mistake: Upon finding the Spanish flu virus missing, Hardison freaks out about it killing 50m people 100 years ago, saying it would be even more deadly today due to the higher population. There's no reason to think so - the death toll in 1918 was massively exacerbated by the aftermath of WWI. Not to mention today we have vaccines, plus most deaths then were actually caused by bacterial pneumonia, which today is easily treated with antibiotics.
Character mistake: The brigadier wears a regimental cap badge. Colonels and brigadiers have their own cap badge.
Episode #6.4 - S6-E4
Character mistake: The character pretending to be Lt. Ellis refers to himself as First Lieutenant. That rank is referred to orally as "Lieutenant", not "First Lieutenant."
Angel of Mercy: Part Two - S1-E4
Character mistake: When Lenore Osgood is speaking on the phone with Charles Wainwright about killing Dr. Hanover, she mispronounces "Larynx" as "Lar-nix."
Looking for Mr. Goodbrain, Part 2 - S3-E13
Character mistake: When Liv and Clive are talking to Chase about Katty, Liv tells Chase he had a cocktail napkin with Katty's phone number on it. However, it was only Katty's hotel room number that was on the napkin, which Liv saw.
Character mistake: When Walker and Satch are in the car looking for Walker's son, Walker tells Satch his son is 17. Afterward, when they are out on the streets, Walker asks some people if they have seen his 18-year old son.
Six Forgotten Warriors Chapter 4: The Six Fight Again - S5-E5
Character mistake: When the Red Skull reemerges from the vortex, he sees Chameleon and acknowledges him as his stepson. However, only moments before this, Kragov explicitly stated that the Chameleon was more like an adopted son to the Red Skull.
The Scandal - S9-E2
Character mistake: Billy has second thoughts about selling his late sister's beach house to a developer who plans to tear it down and build a hotel. Billy tells Ben, "She lived the last years of her life here." But in part 1 of this two-part episode, it was established that the woman had lived in the house for only six months.
Episode #1.3 - S1-E3
Character mistake: Richie Gulliver is referred to as Rory Gulliver on the newspaper headline. As he's supposedly a very well-known Member of the Scottish Parliament, it's unlikely a newspaper would make a mistake like this.
Character mistake: Elliot is sitting on the porch with his mother. He says dizziness could be a sign of a heart attack, or a cardiac spasm that could lead to a myocardial infarction. Elliot is an exceptionally well-informed kid who would know that a myocardial infarction is a heart attack.
Character mistake: Javi states that his relatives have only seen Letty as a blond. But she met Ava in the hotel bar as a brunette.
Episode #2.3 - S2-E3
Character mistake: DS Maxwell comes to Katy's house to interview her but when he introduces himself he says "DI" Maxwell.