Extinction - S4-E1
Character mistake: Happy determines that the nitrogen hydroxide ate through the drum because it was "steel alloy," in contrast with Walter's requirement that it be "pure steel." These terms are inaccurate, and would not be used by technical experts like Happy and Walter. Every steel is an alloy, combining at a minimum iron and carbon; steel with other alloying agents is called "alloy steel," not "steel alloy." Because steel doesn't refer to one specific substance, "pure steel" could never be used to specify a material for a given application.
Character mistake: The Captain yells to Tex to man the "Fifty cal" but Tex goes to a mounted M240 7.62mm weapon.
Character mistake: Doc holds the binoculars the wrong way round. (00:30:20)
Character mistake: When Ruzek and Voight are questioning Wade Henslow (the father of missing girl) at the station, after finding out he lied and set up his own security to find his daughter Adam looks at Wade Henson but addresses him as "Mr. Larson" which is actually the last name of one of the kidnappers they found DOA who got into the gun fight with his security guy, the ex-cop Kenny. (00:21:26)
Character mistake: When Charlotte is going into Henry's dream for the first time, while she is talking, in the background, you see Henry move his head and open his eyes.
Character mistake: When Jack and Kate are in the car discussing the fact that the Russian agents found him because of Mark Boudreau, Kate wrongly refers to him as Martin Boudreau.
Character mistake: The way Henry takes Barry's blood pressure, he will not get any results. Neither the blood pressure cuff nor the stethoscope work reliably through clothing. As a doctor, he should know how to do it right.