As I've done more and more research into MOTU canon and lore, there's a few interesting anomalies that seem curious to me. While all official media can be referenced as canon source material, what about the planned stuff that didn't get made? As new unmade material becomes known by the creators and writers of the toys and shows, it seems that this new stuff is sometimes accepted as official canon by some fans. Here are some examples:
Vintage Eldor, Powers of Grayskull, and Keldor: I forget if there was anything explained about Eldor's bio or what the last two POG mini-comics were supposed to reveal. I vaguely recall some references that Keldor was meant to be the secret identity of Skeletor, though, and this was later used in the 200X series.
The Son of He-Man: This show never got off the ground but the series bible described a lot of new ideas. Dare, King Adam, Queen Teela, Kay-La, Craven, Fork-Lift, Air-Bag, Slob-Boar, Missile-Toe, Ever-Mean, Bug-Eye, Odar, Tongue-Lasher, and Saw-Tooth were all new concepts that probably would've been long forgotten but MOTUC recently created a new faction for this lost era.
New Adventures, Season 2: Jack Olesker has been gracious enough to participate here and gives us a lot of background insight into things that were being planned for this short-lived show. Most interesting of which were the return to Eternia, Drissi and Adam's romantic involvement, as well as the one between Skeletor and Crita.
200X, Season 3: This one seems to be the most widely accepted of the lost canons. While the return of Hordak and the Evil Horde, along with the introduction of She-Ra and Etheria, would've been cool, the biggest revelation for me was that Fisto was intended to be Teela's father. I choose to ignore this storyline but there are a few fans who feel that it should be acknowledged.
So, do you acknowledge these unproduced ideas as canon or do you consider them more like company fan-fic or prototype material that was left on the cutting board?