The Sphere of the "Wounded Lion" manifests in the Gunleon, rather than a person or a combat-based Humongous Mecha to avoid fighting. It would have worked too, if Mel Beater hadn't been killed by Breakers.
Tifa Adil and Eureka quickly become best friends, and Tifa ocasionally gives her ominous warnings about her visions of Eureka from the future. Garrod Ran and Renton Thurston form a Bash Brothers-style friendship as well, and Garrod even gives Renton tips on how to handle a Mysterious Waif girlfriend. Although this gets more screentime in Rand Travis' route, it's present in both routes.
The other prominent cross-series friendship that gets more screentime on Setsuko Ohara's route is Kamille Bidan and Shinn Asuka. Like Garrod and Renton, they also become Bash Brothers, but Z actually points out the differences between them (since the fandom likes to belive Shinn is a Kamille Expy; both are quite different, as specifically pointed out by Amuro Ray and Char Aznable). Kamille plays The Heart, The Smart Guy and is considerate of others' emotions and is saddened and angered by the warfare (his Character Development in Mobile Suit Zeta Gundam and Z take him in a positive direction), whereas Shinn's the Blood Knight and The Berserker who views everything as his enemy (Amuro admits to Char that sensing Shinn's malice when he blocked him from going on a murderous rampage scared him). Shinn's Character Development in Mobile Suit Gundam SEED Destiny was taken in a negative direction, and he only got worse as the show went on. While Z still has Shinn go down the drain for a while, Z doesn't take him to the same extreme the anime did, and it begins rebuilding him as a heroic figure, which truly shows in the ZEUTH route split, where he never abandons the party and goes up against Gilbert Durandal.
The dimensions and the corresponding series merged into the world of UCW as a result of the Space-Time Oscillation Bomb are as follows:
The ACW counterpart of Renton addresses Gainer Sanga as "Gainer-san" and Sara Kodama laughs at him for it. This refers back to the Renton from the UCW calling him "Gainer nii-san", which is akin to "Big Brother Gainer".
Lockon Stratos tells Setsuna that if there's someone who knows how to be Gundam, it's Amuro. In one of the final scenarios where they meet Amuro, Setsuna asks him a few questions about that.
Emperor Zul knows quite a lot about ZEXIS, due to the amount of battles quotes he has when fighting against most of the non-voiced protagonists. He even mentions a few specific things other villains don't normally know. HOW he knows all this is another question entirely.
Gurren Lagann uses an original story to its plot involvement in Saisei-hen (Banpresto didn't use the TV or the movie endings: the original director made a new, unresolved conclusion exclusively for this game). In Scenario 54, Simon uses the titular Humongous Mecha to rescue Nia from the Anti-Spiral, who uses a unit called the "Anti-Gurren Lagann". The Arc Gurren Lagann only appears as a final attack for the Gurren Lagann, while the Chouginga Gurren Lagann does not appear at all.
The translated version of the speech Uther Insalaum recites during the Arclinus Insarius' his strongest attack is as follows:
As the sun shines upon all creation,note Sol Lucte Omnibus
a king's love is for his subjects.note Et Carita Rex Vivito Populus
Kamille acts as a mentor for Setsuna during those trippy scenes when the eponymous machine of Gumdam 00 allows the latter to sense the feelings of all combatants in the battlefield.
Heero is the only non-Code Geass protagonist to know Zero's identity is Lelouch Lamperouge before the big reveal. When Jeremiah Gottwald returns in Scenario 38, Heero and the Wing Gundam Zero is the only unit with the Code Geass cast while everyone else, including the rest of the Gundam Wing characters, head to the Dark Continent.
Saji Crossroad is the second person that comes closest to learning of Zero's identity thanks to his job delivery pizza to Ashford Academy and C.C., but never actively gets any concrete evidence. Also, he's aware something is up with Rolo Lamperouge, because having left the academy following the end of Hakai-hen, his memories weren't rewritten, thus he recalls Nunnally Lamperouge is Lelouch's sister, but he decides to keep this to himself out of nervousness, and also since he has no idea what it means.
The Kedora event from Shin Mazinger traps every ZEXIS member in their dreams, not just Baron Ashura and Kouji Kabuto. This is why various events from each respective series occur.
Like the Protodevlin, Dimensional Beasts are affected by Basara's singing, damaging them in the process. Likewise, the Vajra are demoralized by Basara's songs; this explains why Grace O'Connor loses control over Ranka Lee in the Macross Frontier finale. In regards to Gaioh, whatever Basara's songs are doing is heavily affecting his abilities to control dimensional energies.
Kallen gets a lot of interaction with the Gundam 00 cast. Not only does she visit Saji in his cell on the ''Ptolemios, she gradually gets it into his thick skull about the situation of the ADW. Notably, when he repeatedly calls her out as a terrorist, Kallen doesn't accepts the accusation. Later, she's also responsible for motivating Sumeragi Li Noriega to return, rather than Setsuna, as he promptly leaves her with Kallen, who he thinks can talk to her better because "they're both women". While Kallen believes this is the dumbest thing she's ever heard, she manages to convince her when she tells Sumeragi the story of her mother.
In one of the route splits mid-game, ZEXIS is watching Ranka's concert. Setsuna and Heero are talking about the power of Ranka's song, but Lacus Clyne corrects them and explains her song is not about power but rather a feeling. Unfortunately, both are slightly confused:
Setsuna: "Do you know what she's saying?" Heero: "Not in the slightest."
Saisei-hen ties Charles zi Britannia and C.C. to the plot by making the Code be a mark of the Black Knowledge. After Charles dies in the Sword of Akasha, Lelouch and C.C. discover the ultimate end of the universe, with the former at least trying to think of a way to avert it.
Also, the power of Geass is revealed to share the same roots as the Overmen, an ability that exists so that humans may protect themselves from "Ba'al".
"The Abyss" is a rupture in the dimensional boundary line that connects the various UCW, ADW and other worlds. It only opens at specific times and conditions, but allows safe passage between worlds with correct timing. The Eternal battleship is able to use it to travel to the ADW on instructions from Gen Fudou, who appears to be the only person capable of moving between worlds at will. The Abyss is also responsible for triggering the Anti-Spiral's "Human Extinction System". Because the Abyss is currently acting as a conduit between the UCW and ADW, the system calculates both worlds' human populations together. With a combined total exceeding ten billion (rather than one million from Gurren Lagann), it initiates the second phase.
Every person with access to the Black Knowledge is trying in their own way to resist fate:
Dr. Hell wants to conquer the ADW so he can use all of Earth's means to fight against it.
Wiseman wants humanity to evolve through conflict in order to fight the Ba'al and, failing that, for Chirico to inherit his powers and knowledge to fight in his stead.
Lord Genome knows that the Spiral Nemesis is part of the Ba'al, thus works with the Anti-Spiral to suppress all Spiral beings.
It appears the Zero System is also part of the plans created by Aeolia Schenberg. This implies the system was designed over 200 years ago along with VEDA. In a way, this appears to be a Homage to the Isaac AsimovFoundation trilogy, where the Zero System functions as the "Second Foundation" or backup for VEDA should the plan ever get derailed. On Stage 58 on the Believe Zero/Black Knights Route, once Tieria had gained control of VEDA, Ribbons was Dangerously Genre Savvy to quickly board his Reborns Gundam and destroy Seravee before Tieria could finish using the Trial Field to shut down all the Gagas. However, Heero was able to use the Zero System to interface with VEDA and disable all the Gagas functioning as sort of a backup Trial Field which was something that Ribbons did not see coming. Heero also revealed a Gundam 00 Movie easter egg which identified Ribbons Almark as: Code X1409 EA Ray
Kira has unique battle dialogue (while attacking and evading, possibly taking damage, too) when fighting Gino Weinberg and Brera Stern, where he refers to them by name; Gino returns the favor (instead, he refers to Kira by his full name). All three characters are voiced by Soichiro Hoshi.
Mikhail Blanc doesn't think Lyle Dylandy is fit to replace Lockon since he isn't a dedicated sniper, more so since Mikhail takes it upon himself to pick up the slack after Neil dies. Following the scenario where Mikhail, Gain Bijou and Lyle needed to destroy a Dimensional Beast from long-range, Lyle comes through perfectly and decides he's fit to take over after all.
The death of Nena Trinity in Saisei-hen can occur in different scenarios depending on whether the player chooses to trust Zero or not. If the former is chosen, she dies in Scenario 51; if not, Scenario 52. What makes her death different from Gundam 00 is Setsuna wonders what she's doing at the abandoned satellite where he's supposed to rendezvous with Wang Liu Mei (in the anime, the appearance of the Throne Drei was a surprise). ZEXIS witnesses Nena assassinate Liu Mei as she proclaims the real relationship between Liu Mei and Hong Long (in the anime, no one finds out about this). Even her dying words are slightly different, as Louise Halevy tells Nena she knows she doesn't want to die this way AFTER dealing the lethal blow, while Nena is coughing up blood.
The movie within amovie from A Wakening Of The Trailblazer is parodied in Jigoku-hen, with a unique map, characters and units (such as Mazinger, Gurren Lagann and Shin Getter), but is non-playable. In-Universe, viewers are under the impression Celestial Being has access to Super Robots - if they see something like Godmars in Real Life, they'd believe it's part of the organization. Jigoku-hen also gives names to the pilots in the movie: Setsuna -> Michael; Lockon = Warren; Allelujah = Jennifer; Tieria = Olson.
After the the battle on either route, Ryouma is hired by Jindai High as a security guard/assistant janitor. Apparently, adventuring doesn't pay all that much.
Amalgam pops up a lot, working with Martial and Geminis and so on, and A21 and Sousuke tie in to the Endless Waltz stuff.
Kamille, Banagher, Amata, Shinji, Alto and Kouji bust into the women's hot spring in a enactment of a scene from Full Metal Panic? Fumoffu. However, Gates appears out of nowhere and ruins their fun.
Beck and Kan Yu are now Gauron's lackeys in this game where those two will usually show up along with Gauron and maybe Gates. They also get Firebug to follow them because Gauron made them work for him and that they were out of a job.
Chidori's whispered knowledge apparently gives her knowledge of black history; She's the first person to mention the Axis drop, before even Char mentions it. The ZEUTH people recall seeing this in the black history stuff back in Z1
At onw point, Chirico goes after Fyana with CC. Teitania shows up, they fight. Gauron is working with the cult from Shining Heresy. Chirico is wary of Fyana's safety so he leaves her with the cult.
Graham Aker takes a page from Zechs Marquise and calls himself Preventer "Lightning", a Shout-Out to Zechs' own Preventers Code Name "Wind". If Graham is in a support attack with Zechs, he'll refer to the latter as Fujin ("God of Wind") and himself as Raijin ("God of Thunder").
Shin Mazinger plot is takes ideas from Shin Mazinger Zero. They speculate what would happen if Kouji loses control of the Mazinger and if the Photon Power kept leaking. on that note Zeus battle was fun, they also mention Tetsuya again and Yumi mentions of a possible another dimension Mazinger existing in their world. because Brocken had to run from a battle against a Mazinger and he wanted revenge against Kouji ( 2nd stage event) so he attacked him, Kouji notes that he doesn't understand why Brocken wants revenge, Sayaka reminds him he did beat Dr.Hell who went into hiding. Oh and Viscount Pygman is dead.
It turns out that all the rank and file Mycenaeans were killed by Gaiou, he DIDN'T kill Hades and the 7 Generals
Hades and Zeus appear in the present time because Baron Ashura kills him/herself.
Hades said that if Z-Bl UE can't beat the Kedora made with the brains of the Invaders, how could they hope to beat the Baal army?
At some point, Mykage's forces will attack Hades' and vice versa.
At one point, Kouji has a hard time against Hades. Go and the Shin Dragon shoots him with Getter Rays and Mazinger Z powers up.
As a Shout-Out to Zeta Gundam, Kamille becomes upset when a student from the karate club at Jindai High calls him a girl. He proceeds to beat him senseless, a reference to him doing the same thing to Jerid Messa.
Neo Zeon in Jigoku-hen is primarily based on Char's faction from Char's Counterattack. This causes problems with Marida Cruz, as she comes from the original Neo Zeon faction created by Haman Karn in Mobile Suit Gundam ZZ, which doesn't appear in the Z series. Instead, Marida is more or less a "prototype" of Elpeo Ple; her history as a sex slave is glossed over.
In-Universe, conspiracy theorists state the Mineva Lao Zabi representing Neo Zeon is a fake because she's too young, given the time frame between Z and Jigoku-hen. Naturally, any person who has read Gundam Unicorn or watched its Animated Adaptation knows Audrey Burne is the real Mineva.
Mykage uses the Vajra as mooks because Mykage brainwashed the Vajra with his song.
Mykage kidnapped Ranka and Sheryl in one of the NGE missions and proceeds to use their songs to power the Evil Aquarion in a later scenario. An angry Basara says that their songs have been twisted by Mykage.
Jin's first contact with women are the one in Z-BLUE He thinks that all women are immortal, that they are able to command the battle while drunk and violent, and that they are hard to understand.
Jin isn't trapped in a frog, and Kagura and Zessica are actually be allowed to interact so Zessica getting over Amata for Kagura will actually not be forced and contrived.
The original Aquarion was stored in Central Dogma within NERV along with Lilith.
The Z-BLUE pays a visit in Paradigm City, which results in Aoi vs Schwarzwald, then Gunbuster to the rescue.
Roger essentially reverts to living out the dream state he was in during Episode 14/the first episode of Big O Season 2. Hobo Roger spends a good part of the game wandering around Paradigm until Dorothy finally finds him, he suddenly remembers who he is, and he becomes Roger the Negotiator once again.
Big Venus is involved with the incident 12,000 years ago that Zero and Gendou and other people who actually know what's going on talk about. Paradigm City is supposedly a trial run of the time prison. The wasteland outside the dome is the result of the nuclear winter caused by a parallel Char's Axis drop.
Big Venus came into conception because that jerk Gadlight managed to give Angel that "push" to go ahead with it.
Big Venus works like Zonuda. It deletes your units after the fight.
In the Alternate SpaceLabyrinth, Z-BLUE experiences their idealized world. In a twist, the Labyrinth forces Gundam characters to experience nightmares; for the most part, the worst elements from their shows' respective canon storylines:
Setsuna in despair
Shinn' fury over Kira
Amuro and Char bickering against one another during the Axis Colony Drop
Ryouma shoots Simon with Getter Beam to give him a power boost needed to combine into the Chouginga Gurren Lagann
As per its series, the eponymous Tengen Toppa Gurren Lagann is the size of a galaxy. To justify how the rest of Z-BLUE can fight the Anti-Spiral and the similarly, galaxy-sized Grand Zamboa, Spiral Power affects all of their respective Humongous Mecha, rendering them into galaxy-sized versions of their normal units. This is designated in-game with an infinity symbol as unit size.
Alternate Armageddon Ryoma mentions that the UCW Getter Team has "vanish[ed]"
Axis just fulfills yet another of Ba'al/Anti-Spiral's attempts to drop something onto earth and gives Simon his moment where he promises Nia to save her and we get to see the real Nia for a short moment.
If Ryouma, Kouji or Simon engages the Anti-Spiral, dialogue reveals the latter is an ally of the Mycanae Empire and is supposed to guard the titular "time prison" to ensure organizations like Z-BLUE does not exist.
Jigoku-hen is the first SRW since Super Robot Wars Compact the Final Boss is not an Original Generation (Shikuu is the Post Final Boss), but the Anti-Spiral with the Grand Zamboa, due to it being the authority behind a "battalion" of the Ba'al, having half of the antagonists in the game under its command. Essentially, Jigoku-hen is a lead-up to the encounter with the Anti-Spiral.
The Baldios storyline continues after its "interesting ending" in its home series and goes into the movie plot, suggesting this is how it was supposed to be all along. Z makes a note of this in Baldios' encyclopedia entry.
Files uncovered after Z was hacked include Amuro's voice files for supporting Usso Evin and Judau Ashta in combat. Considering the things current SRW producer Takenobu Terada has said in the annoucement of Hakai-hen, both were probably considered, but only Mobile Suit Victory Gundam is implied to be in a future game and Mobile Suit Gundam ZZ seems to have been dropped due to story issues (it can't happen if the Zeta Gundam: A New Translation trilogy occurs) and the agenda Namco Bandai and Sunrise has for it.