Well Bargained and Done - S1-E2
Character mistake: Tybus says he has a lance of 5 mechs. In Battletech, a lance is 4 mechs. While a Clan star does have 5 mechs, Tybus is an Inner Sphere character.
Continuity mistake: Just before the robbery, Jake throws some water bottles and a flashlight over a small mound into the bushes, to hide them from the thieves. But when Mimi later picks them up, they are much closer to the truck, and on the other side of the mound. In fact, the bottles and flashlight would have been in plain sight for the robbers where she picks them up.
Plot hole: "Sight Unseen": Wells has the key to Lori's shackles. Weston, who knows this, knocks Wells out, but instead of taking his keys, uses a completely unnecessary (and considerably more difficult) set of bolt cutters to break the leg cuffs. (00:32:30)
House of the Rising Son - S1-E2
Continuity mistake: Near the end of the episode, as Klaus is watching Hayley sleeping, Hayley changes from sleeping on her side to sleeping upright in closeup.
Continuity mistake: When the lab equipment shorts out after the earthquake, the unconscious Major Brothers is lying with his head propped up against the wall. But when Hamilton reaches him in the next shot, he's suddenly lying flat and is nowhere near the wall. (00:21:45)
Revealing mistake: When Logan goes looking for Max at Jam Pony, as he starts talking to Normal there is a woman in a blue jacket with a black-and-yellow bike helmet walking behind him. She travels past the group and can be seen heading for the lockers behind OC and Sketchy. After Normal says, "I can't help you," the same woman walks behind Logan again, going the same direction. (00:16:55)
Continuity mistake: It is established that having matter from one universe in another causes it to deteriorate, but the parallel universe doorway closed, even though the photo of Ben and Buster is left in the alternate house. There was brief panic that the chaos wasn't over, when they thought Buster had brought a new collar from the alternate reality, but the photo was forgotten about and the worm-hole thing closed, despite the photo being on the wrong side.
That Little Old Matchmaker, Martin - S1-E12
Character mistake: In Bill's office, after Tim talks about the acoustics in the building, Bill calls Tim "Bill." (00:15:51)
Continuity mistake: Towards the end of the motorbike scene, Matt performs a wheely and overtakes Echo. In the following shot Echo is in front of him again.
Factual error: When the presidents are coming together, there are pictures being taken with flash photography, which would not be possible in a world without electricity. (00:34:15)
The Battle of Central Park - S3-E6
Character mistake: When Justine Feraldo looks at the checkpoint feeds, she says that the Strigoi have overrun the checkpoint at 116th Street and 110th and Amsterdam. But the feed says 118th and Amsterdam.
Map of the Seven Knights - S5-E10
Factual error: The Czech crime database (which appears to be an official Czech database) is headed 'Czechoslovakia'. Czechoslovakia has not existed since the Czech Republic and Slovakia separated in 1993 and neither country uses the term any more.
Continuity mistake: Whenever Banner changes into Hulk his clothes rips, only his pants stays on. But when Hulk changes back to Banner, he suddenly has all his clothes on, no rips or tears at all.
In Too Deep - S5-E8
Plot hole: Carter is apparently just learning about Feynman's Day, which Allison explains as "Eureka's version of April Fool's Day." It's highly improbable that Carter could have lived in Eureka for five years and still be oblivious of this, especially given all of the hijinks that happen.
Sins of the Fathers Chapter 1: Doctor Strange - S3-E1
Revealing mistake: When Mary Jane and the other servants of Baron Mordo are flying through the city, they literally disappear into thin air. Probably a problem with rendering the 2D animation within the 3D animation. (00:01:00)
Character mistake: When Ginnifer Goodwin leaves the supermarket to go the parking garage, the green sign says 1 hour parking Customer's Only. It should say Customers Only, without the apostrophe.
Continuity mistake: Invasion 2021 Season 1 Episode 10 While riding in a car with Hitomi's father, he recalls that she loved a compass she had. She would take it everywhere and loved to follow the red arrow north. But later, when Hitomi's girlfriend finds the compass among her things, the arrow is black with a white tip.
Revealing mistake: As Delta Tango 19 takes off from the airport, there is a shot where it is actually landing. This can be seen from the fact that there is no runway behind them, as it is in front of them.
Factual error: There is a periodic table shown in the background of the lab, showing an accurate periodic table as of now. During 1945, at least 21 elements had not been discovered. (00:17:40)
Continuity mistake: During "Brand New Day", at one point, Dr. Horrible stabs a picture of Captain Hammer attached to a dartboard with a handful of darts, all right in the center of the picture. A few shots later as Dr. Horrible sits, suddenly the darts are far-more spread out. (It's in the background and can be hard to see, but it's noticeable.)