Character mistake: Nicole Wallace has murdered and stolen the identity of Professor Elizabeth Hitchens, who was Australian. While speaking to Detective Goren she refers to her life in Melbourne, pronouncing it the American way : "Mel-born." No Australian would do such a thing - it is pronounced "Melbun." A detail-obsessed knowall like Goren would pick up on that immediately.
Character mistake: Early in the episode, Keith pages JD from home to the hospital. When JD arrives, he asks Keith what's the big emergency and Keith asks if he wants the patient to be prescribed unfractionated or low molecular weight heparin. JD gets angry and says that they're the exact same thing. This is in fact completely incorrect. Low molecular weight heparin is made from fragments of unfractionated heparin. They have different effects in their metabolism, half life and dose monitoring (unfractionated needs a blood test, low molecular weight doesn't). The choice between unfractionated and LMWH is an important clinical decision and should not be dismissed as "the exact same thing".
Character mistake: 23rd minute. Jack meets the female assassin in Anderson's apartment. She demands that he show his credentials. Jack says he's with CTU on a provisional basis and therefore he has no badge. The agent that came with Jack confirms that. Yet, in the 13th episode (minute 14) when he enters the sports shop with Audrey's husband, he shows his CTU badge to the owners in order to prove that he in fact is a federal agent.
Character mistake: While Clark and Chloe are at Daily Planet, Clark asks her what is wrong with her mother. Chloe responds that her mother left when she was twelve years old. In the episode Lineage, Chloe and Clark are looking for Rachael Dunleavy and Chloe says her mother left when she was five.
Character mistake: In the scene where Captain Sobel is inspecting the soldiers at the beginning of the episode, he goes up to Sergeant Lipton and notices something wrong with his chevrons. Well, in that part, Sergeant Lipton is not standing correctly in the position of attention because he is sort of slouching and his head is in front of his shoulders and the correct position of attention is standing straight up and having your neck behind your shoulders. If he was in the real army, he would have gotten a punishment for not standing at the correct position of attention. (00:09:30)
Character mistake: When Sav asks Ali if she wants people to think she's not good enough for their family, Ali accidentally calls Sav "Ray" when she responds: "Yes, Ray, that's exactly what I want." Raymond "Ray" Ablack is the name of the actor who plays Sav. (00:17:31)
Character mistake: In season 4 episode 13, "Tuesday," when Marshall is meeting with Ulrich, he is both able to understand and reply in German. In season 5 episode 15, "No Hard Feelings," Marshall almost misses the opportunity to change the street light from red to green, because the text is all in German. Jack has to tell Marshall which word is green, indicating that Marshall does not understand the German language.