Now we all know this, any of us who are familiar with more than one (or in some cases even one) work in any given timeline, especially all the UC fans out there. So I'm not saying anything new, but hey. I'm sayin' it.
This is such a long rant that I'm dividing it into sections for anyone who wants to read part of it, but not suffer through it all.
Essential Problem: The Universal Century
If we examine the progression of canon in Gundam in general (as I believe it is supposed to flow) you start with the original work. For ease of reference's sake, and because it is the best example of retconning, lets take Mobile Suit Gundam for example. The series airs. The events depicted in the series are canon. A little while later Yoshiyuki Tomino writes the Mobile Suit Gundam novel trilogy, something free from the influence of Sunrise. As Sunrise has ultimate control over what material is accepted into canon, and in most cases animated works ALWAYS take precedence over written ones their word is law.
So the novels do nothing for UC "canon."
Then we have the Mobile Suit Gundam film trilogy, this trilogy rewrites the canon established by the series, while many events are the same are minimally altered, some are simply absent or very different. The material which occurred in series, but is not included in the films is still considered canon, unless it contradicts that which is depicted in the film. While fundamentally the same, significant changes are introduced in the films. One very notable example is that M'Quve does not launch a nuclear missile when he retreats from Odessa and moreover, he doesn't die, at least on screen. Even appearing on Kycillia's Zanzibar's bridge at points after his death in series (though he is absent for the later scenes with Gihren and Char). This causes a significant potential ripple, so to speak.
Despite this and other changes, the two are essentially the same. Enter Zeta Gundam, airing later than the films it can clearly follow either, as the films are accepted canon it would seem to follow them, though it is not explicit whether or not it does. The series resolves, etc. ZZ follows, making no changes that are significant to prior specifically per-existing canon.
Somewhere in here Tomino writes several more novels which are accepted into novel canon, but not anime series canon. Sounds fine. Here is where the real problem starts.
Char's Counterattack: The First Weave of Seperate Canons
Next comes Char's Counterattack, wherein we say a radical shift in the character of Casval Rem Daikun fomer that of Quattro Bajeena to that of the reborn Char Aznable. The change is consistent with his major character flaws (holding grudges, not letting anything go, becoming obsessed and putting his own personal agenda before that of others) despite this it is still an extreme change in attitude. There is no bridge or explanation in this canon as to how we got from the Char of Z Gundam to the Char of Char's Counterattack.
But wait there it is... in the NON CANON novels!
Well that seems to be a bit of a double standard. Also these novels don't mesh with the original trilogy wherein Amuro is ALREADY DEAD! So novel canon is subjective. Some novels align to the anime, other novels to eachother and not the anime, this is only the beginning of this confusing trend.
Enter the retconning.
Gundam Sentinel and MSV - F91: The Continuity Begins to Crack
Gundam Sentinel, and MSV if you want to get technical introduce a host of elements that mesh poorly with existing canon. Now they can work with it, but not without finagling. Take for instance the Z-Plus and FAZZ. If these suits existed before the end of the Gryps Conflict, or even prior to the war with Axis why is there no mention of them? Or hell, why not ship the Argama or Nahel Argama a FAZZ (or two) and a Z-Plus (or three), why make an "ultimate machine designed for power with no regards to the cost" if you already had the same thing... with more armor flying around in pairs? Why do variants of a machine principally designed by Kamille Bidan exist in a short span while he is preoccupied?
So far things have gotten shaky, but remain on fairly solid footing, they make little sense, but do not contradict one another per se. Now we have War in the Pocket, this was more or less good as something set in the middle of existing events can be. It does introduce a new Gundam that apparently existed during the One Year War, but it was experimental and by the time it was pretty much on its feet the war was over. Makes a fair amount of sense. We have several other mechs that seem technologically superior to those in the original series, but there are a lot of reasons and none are too high tech (though the Kampfer is amazing).
Now we have F91. F91 is the first far and away series in a very different time than the others. It works fine, no changes to canon.
Gaia Gear - 08th MS Team: Slippery Slope
Between Char's Counterattack and V Gundam Tomino writes the Gaia Gear novels set in the same time frame as V Gundam. The novels can be assumed as canon up until V Gundam came out and contradicted them. Personally I view Gaia Gear as the real canon as the future presented by V Gundam is just... depressing on multiple levels.
Then we have Stardust Memory. Ahhh, Stardust Memory. Apparently there was some unheard of ace from Zeon dubbed "The Ghost of Solomon" or some such. He steals a Gundam that had been lying around equipped with nukes and a ship of incredible potential chases him while carrying a Gundam that is likely faster than the Zeta, by a good margin. Apparently it also has a huge mobile armor attachment. Oh and Solomon got nuked. Best of all, there was a colony drop on the Earth at a point in time when no one ever mentioned Zeon as being active. That's right, I said a COLONY DROP! You would think that that might be worth mentioning. Well at least it was an excuse to create the Titans, at least this OVA had SOME story tie in.
I admit to not watching the compilations for any of the OVA's those also likely contradict what's here, so that's another factor.
So no, canon has not be self-contradicted in the anime, just stretched, increasingly so.
08th MS team does little to affect canon, other than the fact that there were MORE Gundam's during the One Year War, the rumors that the Feddies only had one were greatly exaggerated. At least they are ground use only and suck really bad (for Gundams) this makes them more endearing, but still aren't GM's good enough for grunts? Way to kill the rank and file feel. Then there's the Apsalus, well Zeon mobile armor, you can add lots in the middle of the past without really messing with things. In brief they all posses impressive firepower... and nothing else at all, though they do have particularly poor defense. The main problem canon-wise with this series was the GM snipers. They were introduced in War in the Pocket and were... GM's with sniper rifles, however in 08th MS team they apparently are GM's with a long range beam that can easily shred ships and mobile armor. Okay, if the Federation had these, why did they never use them? Or incorporate that tech into a Gundam of the era? Also, if these existed, why even bother with mobile armor... though that question should be asked even without them.
Zeta Gundam: A New Retcon - How the UC Ends Here
Now we have no anime UC for a while, up until Zeta Gundam: A New Translation. The irony of this title aside, it further retcons and contradicts existing canon, it in the most severe way. I admit I have not yet seen these films for three reasons:
1.) The fact that they recycle twenty year old footage. This was somewhat acceptable in the first compilation when the footage was from three years prior, but twenty? Zeta was a beautiful series production value-wise for its time, but twenty years? This is unacceptable. Cheap, lazy, tacky. Just to add fuel to the fire they had Gackt do all the openings. Nothing wrong with that, but hiring Gackt for three numbers probably cost more than it would have to reanimate all those recycled scenes. Not okay.
2.) The ending. They gave Zeta a happy ending. WTF? Zeta is about depression. It's about an ending where most of the cast die and the tortured protagonist goes mad. That was what made it awesome. The sense of hopelessness and depression when you realized that Kamille's mind simply snapped. It was... incredible. Giving it a happy ending just isn't right and moreover...
3.) It SERIOUS screws up canon. Kamille remains sane. Okay, that's fine. No I didn't really want him to remain insane, but part of what made Z and ZZ so interesting was watching him at the beginning of Z to the end of ZZ. Oh gods, that poor boy. With Kamille being sane, Axis being defeated and this being the new canon that means that ZZ Gundam NEVER HAPPENED!
It also means that for that matter Char's Counterattack likely never happened.
At this point the canon rewrite is rather severe, no longer is it a mobile suit that seems to be a bit of an anachronism it's half a timeline removed.
The effects of this become progressively more confusing.
Gundam Evolve: Quess Lives!
In Gundam Evolve 05 – RX-93 ν Gundam, Tomino proceeded to rewrite a history that A New Translation likely removed from canon - that of Char's Counterattack. Evolve 05 depicts Amuro as convincing Quess of her mistakes and presents a scenario wherein she survives. I like this, her death seemed meaningless, but it is a major canon rewrite, not A New Translation level, but severe nonetheless.
Gundam Unicorn: It Never Happened
Last but not least, not least at all is the biggest contradiction: Gundam Unicorn. This I also have not watched (and won't until it's finished), however I don't need to know much about it to realize the essential flaw it introduces. That flaw is named Marida Cruz.
I love Puru. I really do. PURUPURUPURUPURU!
The problem is that Evolve 05 and A New Translation are "canon" this means that ZZ Gundam never happened, this means that Glemy Toto never entered a position to create the Newtype Army and thus the clone known as Puru Twelve aka Marida Cruz. Therefore Gundam Unicorn could never have happened.
This is a serious continuity problem. Novel continuity explains it up until the actual Unicorn OVA in which case the concept of "novel canon" goes straight out the airlock. So now, being the most recent animated work, Gundam Unicorn IS canon, which means that A New Translation cannot be, even though it rewrote canon, now the "new" canon rewrites the middle era canon with the old canon.
UC: Like a Rope Made of Separate Canons
Hence we realize that Gundam canon isn't a straight line, or even a line that has been amended and rewritten, it's a series of interconnected laces that weave together intersecting, then diverging and then meeting again, sometimes with a new thread. The "canons" don't even relate to eachother. D can rely on A which is contradicted by B, which is a perquisite for C, which is contradicted by D, even though E requires both A and D to be true.
A complete and utter mess!
This is why Gundam continuity is a complete and utter mess, the worst part is this is all just with information, loads of contradictory information, all of which is "official".
It's a nightmare.
Gundam... Sunrise... Continuity... Money...
In a nutshell it is an all too common facet of Japanese fiction, particularly anime, particularly mecha anime (don't even get me started on Shounens). The bottom line is that it is the effects of a company that markets toys trying to bring in as much capital as possible by having the greatest number of "official" products possible.
I understand this, but still in bothers me.
With this kind of aggressive approach, and it's increasing proportions no series is safe as even when airing, official manga and side stories are created that often contradict or at least radically alter the core of the timeline. This is a systemic problem. It goes beyond the scope of UC, though less often in animated works (the retconning of the tier 1 Gundams of Gundam Wing in endless Waltz to be the new Hajime Katoki redesigns of their original machines is a good example of the second of only two animated series in one continuity managing to do an enormous retcon).
The Stupid Reason for this Long Rant
An admirable example of an attempt to fix such problems is New Mobile Report Gundam Wing Endless Waltz: The Glory of Losers. The depressing fact however, is that as this is not an animated work it will never be regarded as being as canon as the series, unless Sunrise tells us otherwise.
Anyway, just tangented to this from Mobile Suit Vs. Giant God of Legend: Gigantis' Counterattack. The idea is honestly quite entertaining, however bringing in a crossover element tends to immediately remove a work from series canon for logical reasons (except in certain planned crossovers and Superhero comics).
This brings up the annoyance of "official" versus "canon" Sunrise is one of the worst offenders. This distinction continues to frustrate me.
Now on to something more productive.