Giganta tells the Justice League that Darkseid said he'll come to invade Earth, but Darkseid said that on Apokolips, after he destroyed Luthor's ship.
The Shining Knight rescues Star Sapphire before being overwhelmed. But when Wonder Woman comes to his rescue Star Sapphire is nowhere to be seen.
At the end of the previous episode, S.T.R.I.P.E. was armored up and confronted the Society villains as they arrive. But here he has disappeared until later when he's in a house with Stargirl where he's suiting up and teleporting out to battle.
Where are all of Darkseid's minions? They were fighting among themselves at the end of the previous episode and Darkseid united them. But here, instead of using his elite units trained to fight superheroes, units like Kanto, Granny Goodness, Parasite, and the Female Furies, Darkseid just sends in parademons to fight even more heroes then were present when he invaded Earth in the Superman: The Animated Series episode "Legacy."
When Luthor is seen outside of the Metro Tower for the first time, Evil Star is nowhere to be seen. Switch to the Justice League, then close-up on Lex. Evil Star suddenly appears behind Lex. Where did he come from?
When Weather Wizard and Killer Frost are welding the ship's panels together, they heat and cool the seams together very quickly. Any welder/metal worker knows that if you cool hot metal quickly with liquid or other methods, it becomes brittle and prone to cracking. To prevent this, hot metal needs to air dry.
When Lex jumped over the balcony, you briefly see him wearing his armored gloves, but then they vanish, and we don't see them again until he confronts Grodd.
When Lex approaches the vessel that Darkseid appears in, he appears to be no more than a few feet away from the vessel.In the following shot, he is several meters away from the vessel.
Trivia: The surviving Legion of Doom members with Lex Luthor at the end are Heat Wave, Toyman, Giganta, Cheetah, Atomic Skull, Evil Star, Bizarro, Star Sapphire, Sinestro, Killer Frost, and Volcana.
The number of Grodd and Luthor enforcers are split roughly in half between the sixty members, but when Frost freezes them, there's maybe ten that were on Grodd's side.
In the shot of the Legion at the end of the episode, the crack in Toyman's mask has disappeared. The crack then reappears in the next episode.
Green Lantern sets the Ion Drive down during his fight with The Gentleman Ghost, but in the next scene it's gone.
How did the Shadow Thief get Green Lantern to Midway City faster than Vixen and Shayera could fly there via Javelin? He's never displayed any ability to teleport and even his new origin doesn't explain how he pulled it off.
During the fight scene in John's apartment, Vixen dives past John and into the Shadow Thief. He gets up and throws her back the way she came, past John again. But then they cut to a shot of Vixen in the foreground and John and a couch are now between her and the Shadow Thief.
As Shadow Thief is approaching Vixen's apartment, Vixen enters the elevator which is perpendicular to the front door of her apartment. We see her running perpendicular to the door, about to tackle Shadow Thief from the right side, but a second later we see a view of her crashing through the front door, tackling Shadow Thief. Her tackle of Shadow Thief should have caused her and him to go sailing past the door, not through the door and into the apartment.
Brainiac 5 rams his ship into the Fatal Five's vessel, penetrating the hull and getting him and Green Arrow inside. The impact must have been tremendous and yet the Fatal Five seem totally unaware their ship has been breached until Brainiac 5 and Green Arrow break through the door into their "lair."
Differences from the comics: 1) Mano has a disintegrator disc on both hands where in the comics he only has one disc. 2) Shadow Last fires blasts of shadow here, but in the comics she can only project shadows to blind. 3) Validus is (more or less) organic but here when Supergirl punches a hole in his chest he appears robotic. 4) Bouncing Boy can't bounce on his legs in the comics.
When we first see Tharok, the metal of his chin overlaps onto his flesh side. In subsequent shots it isn't present.
When Huntress tried to break into the elevator that led to the Metabrawl ring, she tried to use a lockpick on a magnetic card reader. An MCR doesn't have any mechanisms that a lockpick could affect.
The train carrying the Euros to Kasnia is heavily guarded, yet the train is traveling with the armed guards standing inside open doors. Wouldn't it be more secure for the shipment to be guarded inside freight cars that have the doors closed and locked?