It's weird how I'm writing this before writing a review of the Ideon media I actually hold in high regard (namely, all the other Ideon media (animated at least)). This is a relatively pedestrian compilation film, but I want to write up this review to show why you shouldn't watch it. I will briefly go over my major issues, and at the end I will have a list of changes I noted down while rewatching it for my Tomino marathon (trust me, it's still happening). I'll briefly say before starting that if you can't handle the first 15 odd episodes of Ideon, you can watch this film, I just recommend you watch some TV exclusive episodes, namely the Planet Solo episodes (1-9, of which only 1 and parts of 2 and 3 are retained), episodes 11, 12, 14, and then go right to episode 23 and just keep watching from there. That's still skipping a lot of stuff I like, but not everyone can watch a whole super robot show in 2-3 days like me. On with the review.

There will be MANY spoilers beyond this point. If you don't care (I won't spoil the ending here), press on. If you do, please actually read the above paragraph.

I think there's a lot of weird changes here. There's plenty of valid ones, changing where characters die, removing some more MOTW type episodes, things like the sub arc where Lou catches the measles, I understand these despite liking a lot of those episodes. What I come to question is the cutting of things like Gije's entire character for the most part. In the show, he is basically Zuko (I'm sure most people get this one), a man constantly going on about his honour and chasing after the main cast, leaving devastation in his path, so him turning to the side of the Solo Ship is a stark change in his character. It is a surprise both for the characters and the audience, so when the film does it, they have to completely redo his scene. Gije has to actually explain who he is, he hasn't had physical confrontations with Cosmo and Bes, he hasn't been responsible for destroying planets, he is just some dude. So everyone's just like "Cool man, welcome to the team" (except Kasha, since she's a sociopath), and that's kind of a thesis statement for the film as a whole.

While it gives plenty more to Harulu and Mayaya, it falls apart on every other character, with plenty of characters just not appearing. I mentioned some episodes being completely cut, and yeah, they're just gone, no matter how important they were to Cosmo's character, or to deepening Bes and Karala's relationship, or to really showing how devastating this continued battle is. It sort of robs the show of its soul, and I can't fault it for this because they clearly didn't expect people to watch this compilation film as their only engagement with the series. But, people are doing that now. I have told people to do this, and I lament having done that. I will never recommend this film ever again probably, because it just robs you of the Ideon experience. That's about all I can say on this film, below are my notes I posted on discord, if anyone notices some inconsistencies, please let me know and I will fix it.

• -There is a new opening that goes into the title card, featuring a Buff Clan ship flying through space to Planet Solo
• The movie moves past the first few minutes of the show and goes right to Gije's crew discovering the Planet Solo migrants
• Another section, one that further develops characters like Bes and Cosmo from around 6:59-9:55 (Episode 1)
• During the first encounter with the Buff Clan, many smaller scenes are cut, including all scenes establishing that the guy who gets crushed by falling debris is Cosmo's father
• The above results in an interesting change, as some scenes of Cosmo driving were inserted to be during the initial attack, rather than having him be there for it
• A scene from episode 2, where Gije wonders why they never noticed the Earthlings before, is spliced into the episode 1 content, before Ideon has awakened
• Much of the initial Buff Clan fight is cut to streamline it for a film pacing
• A major change occurs at 7:55 in the movie. Both Cosmo and Deck are not only aware of the Sixth Civilization relics, but also know that the Ide Gauge responds to children
• In the film, Cosmo notices the Ide Gauge changes colour to a light red when all 3 begin moving
• the first scene of Ideon forming is very clearly either remastered or reanimated
• There is more chatter from the Buff Clan aliens comparing the Ideon to the "Great Giant Ide"
• there is a new scene where Cosmo, Kasha, and Sheryl talk on the comms of the Ideon and establish, weirdly enough, more lore, such as the Ideon functioning on a control system Sheryl's father implemented
• Bes' meeting Karala in episode 2 is cut, as are multiple other smaller scenes
• the Ideon barrier is visually established earlier
• Lou and the rest of the orphans aren't present for the second Ideon battle, as the second battle has now been merged with the first one (this is especially odd considering the reveals the second film hinges on)
• the electric wires that the buff clan often used against the Ideon are shown in the first fight, far earlier than in the show
• Many scenes involving Gije, Karala, and Bes are cut as a consequence of this shifting of battles, with episode 2 and 3 being almost entirely cut
• The Solo Ship leaves Planet Solo immediately after the first fight, completely cutting episodes 4-8 and half of episode 9
• a new scene is added explaining how Bes and the others got from the Ideon to the bridge of the Solo Ship
• Karala and her guard (Mayaya) are discovered as aliens because they weren't found on the list of colonists, rather than Bes discovering this fact through Karala
• the above scene is in fact, completely original to the film, including a film original instance of sociopathic Kasha saying Karala should die for being an alien
• the fact that Cosmo's father is dead is established 20 minutes into the film, with Cosmo having never been informed of this fact beforehand, and everyone acts like he already knew it
• rather than Gije putting a tracker on the Solo Ship, Mayaya has a biological transmitter on her. Karala's bodyguard also ends up living longer, as there is no chance for her to die while on Planet Solo
• Harulu is introduced earlier, right after the Solo Ship crew abandons Planet Solo, in a new scene (this also removes the second Buff Clan soldier Gije teams up with)
• there is a new scene where Bes explains the legends of Ide to Cosmo and Kasha, rather than the original interrogation scene with Karala (as a consequence of this, the legend of Ide flashback is moved to later in the film and is shortened)
• every scene involving Karala's imprisonment is new
• Mayaya is killed by Lotta, instead of dying trying to free Karala
• Moera gets a new scene telling Karala that many people on the ship would love to see her die
• the scene of Karala's arm getting shot is cut, yet she still retains the bandage when Lotta is shouting at her in the forest
• I'd like to point out that all of the Lotta stuff above is Episode 13 content, meaning Episodes 10, 11, and 12 are completely cut
• There is a new scene establishing the Ideon cannon earlier, which occurs 29 minutes into the film. This scene isn't entirely new though, as it's a remake of a scene from the episode where the cannon is first used in the main series (which itself was a retcon)
• as mentioned earlier, the legend of Ide flashback is moved, and is in an entirely new scene, with characters like Cosmo and Kasha not being present
• there's a new scene of Karala and Lotta trying to catch chickens
• there is a new scene of Bes and Sheryl talking about going to Earth to use the Gloria computer
• Episode 14, the first "DAMN YOU BUFF CLAN" episode, is completely cut
• Episode 15 is trimmed down to just be Sheryl trying to escape to Earth and failing, with the majority of the episode itself removed
• there is a new scene where, rather than the Buff Clan captain that holds Karala and Sheryl hostage, asks Harulu what to do in this situation, and Harulu says that Karala is worthless to them
• in addition to the above scene, there is another new scene where Harulu mocks Karala and the two touch on whether or not the power of the Ide is real, and why the Buff Clan is scared of the Solo Ship having that power (this scene also acts as a stand in for the cut episode where Karala is cast out from the Buff Clan and humiliated)
• Cosmo's plan to save the hostages (situation mentioned above) is a lot more idiotic (on the part of the Buff Clan for falling for it), as rather than forcing the Ideon to transform after the hostages are freed and they're in the last Ideon unit, he asks the Buff Clan to let him transform the Ideon units before giving them up
• justification is given to having Deck on board the Ideon and piloting it despite being like 9, that being that having a child on board makes it more powerful
• Episode 16, 17, 18, 19, and 20 and the conflicts within regard Cosmo's solitary confinement, Lou catching the measles, and another colony trying to steal the Solo Ship are completely cut
• Cosmo's injury and requirement for a blood transfusion from Karala is moved to occur during the events of Episode 21 (this is due to the Kitty Kitten episodes (23-25) being almost entirely absent from the films)
• Another plot point moved from the above is Karala revealing where the Buff Clan planet is located
• Episode 22 is cut, but it's a recap so who fucking cares
• Bes' dream about the true nature of the Ide is cut down and changed into Cosmo's/Karala's dream (this is done because Cosmo's original dream no longer works without Kitty Kitten)
• Episodes 23, 24, 25, and 26 are cut, with the exception of around 5 minutes of content being moved to different sections of the story (with Kitty Kitten and her planet appearing in the next film briefly)
• The Solo Ship arrives at Earth before encountering Kitty Kitten's planet
• Moera's conflict from Episode 32 is moved to be during the Earth conflict
• a majority of episode 27 is cut, the film only retaining Sheryl accessing the Gloria to analyze the data on the Sixth Civilization
• 28 - 31 are for the most part cut outside of some re-arranged scenes, and the crew never interacts with the Earth military
• Gije hiding himself in the ship and the crew knowing who he is is completely cut, and this means the scene of him crying is removed
• the film ends on the crew abandoning Earth (which is Episode 32 in the anime)

In total, around 22-24 episodes worth of content is cut
In a film that covers 32 episodes of content
Yeah. In addition, I know this isn't all of it, as I was going back through my screenshots, and saw many scenes that were absent in the film, scenes that I really liked, that posed interesting questions, that set up ideas that the series would ultimately cash in on. All I can leave off on is a general feeling of disappointment.