So. In Episode Eleven of Season Six of ther Clone Wars ("Voices"), Yoda receives a mysterious spectral message from Liam Neeson, who has spent the previous seventy episodes being dead. (Liam Neeson has form for this. He played Aslan in the Lion the Witch and the Wardrobe, and had a walk on as God in the still astonishing Rev.) It seems that, as a general rule, when a Jedi dies he goes to join an impersonal, Buddhist after-life in which he is one with the Force. Qui-Gon, on the other hand, has continued to exist as an actual personality.
There is some narrative to-ing and fro-ing: the Jedi Council all lay hands on Yoda like charismatics at a healing service, and then suspend him in an isolation tank. With Artoo Deetoo at his side, Yoda absconds from the Jedi hospital and flies to -- you'll like this -- Dagobah. There he encounters the late Qui-Gon Jinn, who manifests as a cloud of Tinker-Bell-like Pixie Dust. Yoda undergoes a Test under the same tree where Luke faced/will face the vision of Darth Vader in Empire Strikes Back. Yoda's vision is a flashback/flash forward to the destruction of the Jedi and the Senate which happened/will happen in Revenge of the Sith. Having passed the test, Qui-Gon sends Yoda on his way to a planet at the exact center of the galaxy "where life first arose". One hates to intrude on fandom's collective grief, but this is also the planet where the Midichlorians originated. It looks and feels like a very trippy computer game, or possibly a Rodney Matthews album cover. Yoda spends most of the next episode ("Destiny") jumping from one floating pink mushroom to another. He encounters a group of floaty masked Force ghosts, who direct him to the next part of the selection process, which involves confronting and mastering his Dark Side.
It turns out that Yoda's Dark Side is pretty indistinguishable from Andy Serkis playing Gollum; but since Yoda confronted and mastered it some time ago, he isn't detained for very long. So in the final episode ("Sacrifice") he is sent off to the planet Moribund, where the Sith originally originated. In the Secondary Canon they came from Korriban and in Rise of Skywalker they came from Exegol, but here they come from Moriband. Yoda meets a giant Balrog which claims to be the ghost of Darth Bane. He was the Lord who first had the idea of allowing the Sith to die out except for a single master who could pass the dark teaching on to a single apprentice. ("Always two there are.") Yoda then has a complex vision in which he fights Darth Sideous, and again avoids falling to the Dark Side. So the Floaty Force Ghosts agree to share the secret of eternal life with him. They also tell him that there is another Skywalker. This is, of course, what Yoda told/will tell Luke in Return of the Jedi. I don't know what Yoda understands by it at this point: he doesn't yet know that Anakin and Amidala are married, so he certainly doesn't know that she is pregnant.
So: what are we to do with this kind of thing?
It isn't, compared with the best episodes of ther Clone Wars, all that much fun. Not many buckles are swashed and few cracks are wised. The story exists purely in order to paper over some admittedly substantial cracks in the Prequel Trilogy.
In the final seconds of Revenge of the Sith, Lucas pulled out of thin air the idea that Qui-Gon has taught Yoda how to survive being dead; and that Yoda is going to pass the secret on to Obi-Wan. This was itself a fairly contrived attempt to ret-con a small gap in the plot of the Original Trilogy. Obi Wan says that if Darth Vader strikes him, Obi-Wan, down then he, Obi-Wan, will become more powerful than he, Darth Vader, can possibly imagine. Vader is surprised when Alec Guiness's body vanishes. This is emphasised in the comic, the novel, and the LP versions, and was presumably a stage direction in the ur-screen-play. Ben's words to Vader are never followed up. When Yoda dies, his body also evaporates; and we see his Ghost, along with the ghosts of Ben and Luke's Father together in the final seconds of Return of the Jedi. I think Lucas, at that stage, rather intended us to forget the broad hint that Ben's death was unusual and treat dying, vanishing and Force ghostliness as a normal part of the Jedi career path. Yoda's remark at the end of Revenge of the Sith confirms that Ben was indeed a special case, and that dead Jedi don't habitually hang around outside their protege's space ships encouraging them to switch off their targeting computer's. But it's a pretty huge plot point to be resolved in a single line. The cartoon episodes are a valiant attempt to give the ending of the film, and therefore the entire saga, a little more coherence.
Is this kind of plot-hole filling a worthwhile exercise? Some people might think that if you go to the trouble of setting your cartoon in the big blank space between Episode II and Episode III then you owe it to your viewers to fill the space up with Stuff; and that resolutions to dangling plot threads are very much the kind of stuff you ought to fill it with. Other people might say that if George Lucas decided to leave a big blank space in the middle of his composite artwork then David Feloni ought to refrain from scrawling graffiti on it.
This kind of thing arguably compounds the problems inherent in prequels. We know that Vader / Anakin was a good Jedi who was consumed by the Dark Side of the Force: we didn't particularly need three films showing us that fall in slow motion. We knew that Ben continued to talk to Luke Skywalker after he died: we didn't particularly need a new scene which tells us "That's because he had acquired a secret Talking-To-People-After-You-Die power." But knowing that, we didn't particularly need an hour and half of cartoons saying "Finding out the secret, finding out the secret, here is Yoda, finding out the secret."
What these episodes do, fairly successfully, is add significance to the problematic scenes. I suppose one could say that they apologise for them, or in the jargon, redeem them. Yoda's revelation about finding the secret of immortality comes out of the blue in Revenge of the Sith. It is narratively too easy. Eternal life is the kind of thing that sons of God lay down their lives for; not a knack one learns in the same spirit as a new Yoga position. The cartoons show us that Yoda had to go on a full-on Vision Quest to learn the secret. He refuses the quest, meets a mentor, descends into the underworld, faces a number of tests and temptations and rises again with the Boon that will Save the World. So the secret of the Whills was not a random plot device but -- from a certain point of view -- the pivotal point on which the whole saga turns.
"Qui Gon Jin has revealed to Yoda that he must manifest his consciousness after death if he is to preserve the Jedi order" yells the melodramatic narrator. The Floaty Force Ghosts say that Yoda needs the secret because "he is to teach one who will save the universe from a great imbalance". Anakin's destiny is to kill the Emperor; Luke's destiny is to bring Anakin back to the light so he can kill the Emperor; Yoda's destiny is to train Luke so he can bring Anakin back to the light; Ben's destiny is to send Luke to Yoda to be trained... No-one can fulfil their respective destinies if Yoda doesn't learn how to do immortalling.
I like the parallelism between Dead Qui Gon sending Yoda and Artoo to Dagobah; and Dead Obi-Wan sending Luke and Artoo there in Empire Strikes Back. Luke thinks there is something familiar about the place, but it turns out that Artoo has been there before.
We have noted before that Star Wars is presented as a fairy tale; and fairy tale needs a story-teller. There is a long-cherished fan theory that the person telling the story is, in fact, Artoo Deetoo and that he is not always a reliable narrator. Artoo is portrayed as being the barer of the secret plans (with a Secret Mission, no less); and the one who travels alongside Luke to destroy the Death Star, and alongside Anakin in all of his big missions; a close confident of Amidala; an endless source of increasingly unlikely gimmicks and gadgets as the saga progresses. So, naturally, Artoo would spin the story so that he was Yoda's companion on his most important voyage. I don't "believe" this theory, any more than I "believe" that Jar-Jar Binks is a secret Sith Lord. But I am quite sure that Dave Feloni is aware of the theory - just as the Beatles became aware of the Paul-is-Dead hoax - and that he deliberately plants clues for the fans to find.
END OF DIGRESSION
We get a certain amount of new, er, Lore. Qui-Gon says that there are two different Forces: the Living Force, which resides in each living thing in the universe and the Cosmic Force, which is the sum total of the Living Force of everyone who has ever lived. The Midichlorians mediate between the Living and Cosmic sides of the coin. Lucas's early, inelegant scripts for what was still called Ther Star Wars talked confusingly about the Bogan Force and the Force of Others and various other sub-Forces. Qui-Gon, who didn't learn enough mystical stuff to manifest as a Force Ghost is represented by little shiny sparkly things -- which I think are supposed to represent the particles of the Living Force which were left behind when his body died, but have remained separate from the Cosmic Force. Jedism doesn't seem to be in a strict sense pantheistic: the Force is not mystical or supernatural, but a component of the physical universe. There have to be Midichlorians, otherwise we might start to think that the Force was literally God or the Soul.
So, then. A great secret Yoda has learned, and passed it onto Obi-Wan he has. When Revenge of the Sith first came out, I said that this felt like the pencilled-in sketch for a different film. Two competing heresies, passed down from master to apprentice, submerged in the monolithic but moribund Knights of the Holy Space Grail. When the time is fulfilled both the Whills and Sith will reveal themselves and one or the other will take over the Order and therefore the Universe. A far from uninteresting idea for a space fantasy epic; but not the space fantasy epic that Lucas in the end made. It does not magically come into being just because Yoda says "An old friend has found the path to immortality". And it doesn't become any solider because we've seen Yoda playing at Joseph Campbell three weeks running.
It seems to me that there are two ways you can do this stuff. You can look at the existing lore, cartoons and computer games and all, and use them as a plot-creation engine. You can, in effect, ask "Granted Ashoka and granted Luke Skywalker and granted Admiral Thrawn, what would happen if....." The cross-over sequences in the Mandalorian and the Book of Boba Fett may have offended the continuity-averse, but they seemed to me to be stories which are worth telling "What if Vader had an apprentice before his fall; what if she were still living; what if Luke met her?" is a valid and interesting question; and it would still be a valid and interesting question even if Ashoka were not, minute for minute, the longest-standing character in the Star Wars saga.
But the Yoda material is not building new stories from the components of existing ones. It's creating new stories in order to patch holes in old stories, and so far as I can see the hole is not patched. (On no possible view could Darth Vader have known Qui-Gon's secret teaching, so how could he possibly retain his consciousness and attend the Ewok bonfire party with Ben and Yoda?)
And we know the answer. Lucas wanted us to see Yoda and Obi-Wan at the end of Return of the Jedi because it was a nice scene to end the movie on. He wanted to show Luke's Father, back when Luke's father looked like Sebastian Shaw because he wanted to make the point that Luke's quest had succeeded and his father had been redeemed. And then he went back and retrospectively added Hayden Christensen to the cameo, because, well, why wouldn't he? Qui-Gon wasn't there because Lucas hadn't dreamt him up yet. It's more like
So: anyway. There is my model of good Canon versus bad Canon.
Using existing material to create new stories: Good.
Making new stories to patch holes in old stories: Bad.
Ther Clone Wars is mostly good canon. Go watch it.