- Bizarro Episode: Episode 29 "Distant City, Uqbar" is one serious Mind Screw.
- Complete Monster:
- The Radical Destruction Bringer is an entity from deep space bent on the annihilation of the human race. Claiming to be saving the Earth and universe by destroying humanity to trick Hiroya Fujimiya into helping it, in actuality its only motive for seeking humanity's destruction is a God complex and hatred of beings it sees as "insects on a trash heap". In the course of its rampage, among other atrocities, it would exploit innocent kaiju from both Earth and space and send them to their deaths without remorse; brainwash entire cities into rabid zombies; attempt to send an entire region of Japan into the Earth's mantle; and try to cause the tectonic plates to rip themselves apart under humanity's feet. In the end, it would send its Dobishi army to destroy humanity via blotting out the sun and letting them freeze to death in the cold, alongside its enforcer, the Root of Destruction, Zogu. When Earth's monsters rise against it, the Destruction Bringer shows them no mercy and has its Dobishi brutally kill many of them without remorse. Despite its claims of benevolence, the Destruction Bringer is nothing more than a self-righteous hypocrite motivated by hate.
- The aforementioned Zogu ("Fundamental Destruction Angel") is one of two Roots of Destruction, the Destruction Bringer's strongest enforcers. Sent to Earth alongside the Dobishi to destroy all life on Earth, Zogu has the Dobishi block all communications except for the news media so humanity can watch the increasingly hopeless situation unfold and fall into despair. When Gaia and Agul arrive to stop them, Zogu descends while feigning benevolence and atomizing three of her own Kaizer Dobishi. She then reveals her true colors by brutally pummeling the two into submission with sadistic glee before draining their power and revealing to the world their true identities as mere humans. Zogu then falls back to allow her Dobishi to blot out the sun and watch humanity slowly die in cold and despair. When Earth's monsters rise up against her, she has the Dobishi attempt to brutally kill them. When Gaia and Agul manage to return and harm her, Zogu reveals her demonic true form and attempts to crush the two to death. While an enforcer of the Destruction Bringer's will, the joy in which Zogu does so makes her just as bad as her master.
- Once Again Gaia: Gakuzom ("Root of Destruction Sea God") is Zogu's brutish fellow Root of Destruction. Surviving Zogu's defeat and his master's retreat, Gakuzom would begin his own onslaught on Earth several years later. Attacking the peaceful and defenseless Rinar 8,000 feet below, Gakuzom would viciously assault the GUARD sub sent to answer their SOS. Finally making his move and plunging the Pacific into a perpetual storm, Gakuzom attempts to wipe out all life on Earth with his Baiakuhe, with the Root of Destruction attacking Tokyo personally. When Agul arrives to stop him, Gakuzom has his minions maul and restrain the hero while he beats him down himself. When Gaia arrives, Gakuzom devours his entire army and begins brutally pounding the two heroes.
- Ensemble Dark Horse:
- Ultraman Agul and by extension, Fujimiya. In fact, the two were supposed to be retired when Gaia obtains Agul's power but the sheer amount of Popularity Power allows them to return.
- Gan Q for the series' monsters. He ranks up with the likes of Gomora, Baltan, Pigmon, and Dada in sheer recognizability amongst Ultra monsters.
- The series has more recurring non-Japanese characters than any other Japan-produced Ultra Series, so not surprisingly, they've nabbed quite a bit of attention amongst western fans.
- Fan-Preferred Couple: Gamu and Atsuko. The fact that their relationship never resolves by the end is a major disappointment amongst fans.
- Funny Moments: The entirety of episode 35 "Ransom for a Monster". A group of Dumb Crooks find the Monster of the Week's egg and decide to hold it for ransom, pretending to be aliens. They accomplish this by barely changing the name of the iron working company they work for. The funniest part is GUARD plays the entire situation completely straight, unaware it's a scam.
- Harsher in Hindsight: Episode 33 shows an alternate future wherein Team Falcon made a Heroic Sacrifice by killing Aeroviper at the cost of their lives. In real life, one of the actors of Team Falcon, Shogo Shiotani, committed suicide in 2002.
- Hilarious in Hindsight: Chiaki Konaka goes into Kaiju-writing business again three years later.
- Moment of Awesome:
- Gamu schooling the Ace Pilots in how to properly operate their fighters, something they weren't very competent at prior, due to the simple fact he invented the tech they use.
- Gamu figuring out a way to counter Mezard on their way back to base and having a fully fleshed out plan and method to force it into the physical plan where it can be attacked.
- The Earth monsters teaming up with humanity and the Ultramen in the Grand Finale could certainly count.
- Narm: Genshenk's roar, which also combines a cat's meows.
- Tear Jerker: Tsuchikera's episode "The Lake of Sadness" is one of the biggest in the Ultra series.Kondo: Thank, you, Hirano. Because you were there for me, I managed not to lose my heart. Now I'm ready to go to where Chei is. Thank you, Hirano.
- They Wasted a Perfectly Good Plot: The relationship between Gamu and Atsuko is this towards most fans, since they never had a resolution in the end despite a lot of plot buildup in-between them. Such examples can be shown on their similarly Friendless Background, Atsuko growing from a Tsundere towards a more warming personality to Gamu and a minor Clingy Jealous Girl moment in episode 42. The OV (taking place sometime after final) has Gamu resuming his life as a university student and Atsuko returns to her Tsundere mode again.
YMMV / Ultraman Gaia