Revealing mistake: At the end of the episode when Tuco shows up at Walter's house in the backseat of Jesse's car, he tells Walter to get in. As they drive off, the shot pans out to show the street sign across from Walter's house. The sign says Piermont, which is the real name of the street. In the show, the Whites live on Negra Arroyo Lane. (00:48:00)
Plot hole: The very ending scene where Peter (in this version died in the ice as a boy so Walter's wife never met him) takes off some of the dust covers then picks up a toy airplane. The toy airplane he got as a child from ... Walter's wife when she was trying to placate him in an earlier episode for trying to run "home". This toy airplane wouldn't have been his as a child in this version of the universe. (00:42:00)
Continuity mistake: When Jax and his crew meet up with a Hispanic gang to sell them guns and are outnumbered, they run in the station wagon. The run the station wagon through a gate and roll it, destroying the front end, but magically the station wagon's front end appears with little damage afterwards. (00:27:15)
Continuity mistake: When the two factions of Hondo's pirates are fighting each other, the ones who sided with Maul and Savage are using blasters that fire red bolts, while the ones that stuck with Hondo shoot blue bolts. When Hondo persuades the traitors to work for him again and they attack the two Sith, all of the pirates' blasters are now firing blue bolts. This is Star Wars, not G.I. Joe, and weapons don't just change colour like that.
Factual error: Enid, the telegraph operator, exclaims that "He is sending an SOS." However, in the 19th century, distress calls did not include the letters "SOS," It was not until the early 20th Century that SOS was chosen as the international distress call.
Continuity mistake: All shots of the Jeep Cherokee prior to it crashing (and during the process of flipping over) show that it wears factory-optional silver steel wheels of a 'star' style. But as the wreck settles upside-down, it's wearing plain steel wheels (like those found under full wheel covers or on a spare tire).
Factual error: This series uses a beautifully-rendered CGI sequence of New Amsterdam C. 1650 morphing into New York City of the present day. The Native American tribe we see at the start of the sequence, however, never inhabited the New England area. They look more like the Lakota plains tribes seen in Dances With Wolves. The North-Eastern tribes didn't build teepees as seen here, either. The dwellings should be longhouse wigwams made of wood.
Continuity mistake: Moseby shows a 'Mood Hanky' to London, and it turns purple when London embarrasses him. When the other characters reveal their inventions, 'Granny Smith' and the robot feed Moseby a sandwich. Moseby enjoys the sandwich, saying "Mmmmmmm! Cheesy!" Even though he is happy, the Pocket Hanky is still purple.
Factual error: The camera starts out-of-focus looking down a crowded sidewalk full of background actors in period clothes and hairstyles (1973). As the camera racks into focus, Sam is walking toward the camera with many awnings visible in the background - a large blue one reads "24 Hr ATM". Though versions were invented prior to 1973, they didn't come into wide usage until the mid-to-late-80's and certainly weren't available in East Village bodegas at the time of this episode.
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.)
Continuity mistake: After teleporting the villains and heroes to Lex's lair, Lex has his hands gripping a control panel podium in front of him. As Joker begins to speak, it cuts to a closer angle and suddenly Lex's arms change position and his hands are gripping the podium differently. (00:17:05)
Continuity mistake: As Tony is walking over a wooded floor, there is a plant behind a yellow couch in the lounge, and the plant appears to be an orangish brown color. A few shots later as Tony is walking, you see the same plant behind him which is now green. (00:02:05)