Batman Can Breathe in Space: Subverted as Mark has to hold his breath while confronting the alien Allen outside Earth. Beforehand, he asks his dad how he can breathe in space. Nolan's response?
Nolan: That's the neat thing. You don't.
Brick Joke: A father and son visit London's Buckingham Palace, only to be bombarded by what looks like Ludicrous Gibs... only to learn that they are trash bags containing Burger Mart stuff. The son is surprised there is a Burger Mart in the United Kingdom, but it's actually from the United States when Mark accidentally throws it when first discovering his powers manifesting from last episode. The kicker? The father is the same White House security guard from the same episode, planning to take his son to London.
But What About the Astronauts?: A shot from orbit over the Flaxan homeworld shows a space station watching as Omni-Man's trail of carnage devastates their civilization... and then Omni-Man answers this trope by taking out the station, too.
Clark Kenting: Eve explains to Mark that this is a psychological phenomenon. She doesn't wear any kind of face covering with her suit, and her real name is part of her superhero alias — but nobody at their school puts two and two together about who she is, because nobody at their school is looking for a superhero there.
Curb-Stomp Battle: Omni-Man spends supposedly months making an example of the Flaxans' homeworld, starting with their leader, who he rams into buildings until he's reduced to a fistful of meat.
Flat-Earth Atheist: Lampshaded. Donald, one of the Global Defense Coalition's agents, is an atheist. One of the people they're working on while investigating the Guardians' slaughter is a very literal demon. Cecil comments sarcastically on this contradiction.
Cecil: Got a problem with the demon? I thought you were an atheist, Donald. Donald: Th- theoretically.
Foreshadowing: Omni-Man's Pre-Mortem One-Liner to the Flaxans, "Earth isn't yours to conquer", hints at the fact that he is planning to conquer Earth, himself, on behalf of the Viltrumites.
Internal Reveal: After Omni-Man charges into the Flaxan portal as it vanishes, a distraught Mark calls out to his father while the rest of the Teen Team are present.
Rex Splode: Whoa-whoa-whoa. Omni-Man's your dad?
It's Personal: During the second and third invasions, the Flaxan leader singles out Invincible for scarring and blinding him in one eye during their first encounter, and for destroying his protective bracelet (thereby exposing the Flaxans' weak point to the other heroes) in the second.
One-Man Army: The Curb-Stomp Battle Omni-Man delivers on the Flaxan planet shows just how dangerous he is when he supposedly stops holding back. Case in point, he manages to fly at such speeds that each impact with a building causes it to detonate; this is followed by a shot from space of him rapidly bouncing between cities causing multiple nuclear flashes. This is a single superhero's attack against an entire race that borders on, if not already is, genocide or xenocide depending on the terminology.
Papa Wolf: Whatever Omni-Man's agenda is, he makes a terrifying impression on the Flaxans by rescuing Mark from their leader. His Death Glare ensures none of the invaders are getting out of this alive.
Poor Communication Kills: Nobody bothers explaining to Mark who Allen is, only telling Mark when he's coming, and to send him back to space. On the other side of the equation, Allen didn't realize that Invincible and Omni-Man were different people... and that he was inspecting the wrong planet.
Rule of Three: Invincible, then the Teen Team, repels the Flaxan invasion twice. Omni-Man shows up in their third attempt and supposedly takes them down once and for all.
Omni-Man: You don't seem to understand. Earth... isn't yours to conquer.
Year Outside, Hour Inside: The time dilation consists of the Flaxan dimension being the former by "decades", and Earth's being the latter by the day. It serves as an initial weakness that requires them to adapt through new technology. Without it, they age quickly and their earlier generations of weapons corrode from time and oxidization. It works the same way in reverse as well. Omni-Man spends a few hours on their world smashing their civilization to pieces and returns with a full beard.
