Ascended Fanon: In Tinker's Seal, Star Shimmer is implied to be related to a mythical dark lord from the north, referring to the legend of the land of Ultima Mule. However, with the return of the Crystal Empire, scholars theorized that the legend of Ultima Mule was in turn based on the Crystal Empire. When the author was asked if her ancestor was King Sombra, the author decided to go with it.
Goa Trance duo, Genom Screams and Sweet Psy, are big fans of the series, and made some fan music for it around the time Breathing Weapons was being written. Come the companion-soundtrack release of book, the author deemed the songs 'excellent' and had them included on the album as bonus tracks.
For the most part, Ember Roundup was happy with Amber of the Smooze, but admitted using Gusty Lulamoon's younger cousin as inspiration for Princess Sparkler without asking permission and exaggerating some of her negative traits to outright insulting levels, all the while profiting off the caricature, wasn't exactly one of her proudest moments. This was originally revealed in a Gabby Gums article, whose photographer discovered several unsent, rewritten apology letters. Ember would later give a more complete explanation in The Fillydelphia Tribune. The Tribune article would further elaborate that as an apology, not only would Ember donate royalties to said cousin, she intends to include her as a creative consultant in the upcoming Alicorn Amulet.
Kevin J. Canterson rarely gets fan mail for Buffalo Burial Grounds. When he does, he's been rumored to write back and ask for hate mail instead.
Annon N.E. Moose was apparently disgusted with Rail's portrayal in fanfiction as a puppyphile rapist.
Ember Roundup, following the death of Gusty Lulamoon and her discovery that Beatrix Lulamoon had fallen off the map during the last two years. While her work on Tinker's Seal didn't suffer, she did pull out of a planned collaborative project with Steeplechase Moffat, giving him permission to finish off the Colt of the Smooze arc, and concentrated on her work for the Tribune for several months. Thankfully, her friendships with Beatrix and her new partner have done a lot to revive her passion for the series.
As the Blood Diamonds series gets darker and more depressing with each installment, people suspect Ghost Writer is suffering from something.
It was recently confirmed that Rachael Neigh Cook would be voicing Eichelhäher in the upcoming Breathing Weapons animated mini-series.
Hossed: There was speculation that Princess Sparkler's first name, Twinlight, was based on Princess Twilight Sparkle after her name was revealed in some of the previews of Alicorn Amulet. Though claimed to be a complete coincidence at first, when pressed the author stated the name was always intended to be Twinlight, and the name was actually based on Twilight Velvet, fellow Daring Do author and Twilight Sparkle's mother, who Ember interviewed in her early days at the Fillydelphia Tribune and considers a mentor.
On that note, the "newcomer" co-author of Alicorn Amulet, "A. Sparkler Star", was for several months rumored to be fanfic author MagicSpark, due to other unconfirmed rumors of her real identity being at the centre of the Alicorn Amulet incident in Ponyville. This was hossed first by a blog post from her revealing that certain responsibilities would be keeping her away from writing for a while, and again by the announcement of said newcomer being named A. Sparkler Star. Neither of these announcements have done much to end the speculation along these lines.
A rumour that conspicuously hasn't been hossed, despite reaching Epileptic Tree levels, is of A. Sparkler Star being a teenage Ponyville resident by the name Sparkler. This is largely based on her being an eyewitness to Lulamoon's reign in Ponyville, and also Muffin Parcels' adopted daughter, regardless of the fact that she has no direct connection to Roundup or the Lulamoon family.
Old Shame: The wildly unpopular Mareval Comic series for creator Alan Moooore.
Buffalo Burial Ground is this for Kevin J. Canterson.
One of Us: Princess Celestia herself has admitted to enjoying the series, and introduced Princess Luna to it upon her return. The latter was also reportedly very excited to meet Ian McCloppen on the set of Legacy of Nightmare Moon.
Recently reformed Spirit of Chaos Discord has also claimed to be a fan of the series, and has mentioned on numerous occasion to be willing to appear as himself (or, failing that, Starswirl the Bearded for some reason) in the films. There has been no statement one way or another from anyone involved in the films regarding this as of yet.
Promoted Fanfilly: Just about all of the Expanded Universe writers, really, though some of the more recent ones were already well-known in fanfic circles, in particular L. Heartstrings, author of Daring Do and the Minotaur's Maze and contributor to Tinker's Seal and Mirror Pond, who was previously known for a number of crossover fics and Darrincon appearances.
Also, Muffin Parcels collaborated with her idol Steeplechase Moffat on Universal Cracks, which both authors have confirmed is intended to be in continuity with her earlier Zapapple Tock Alternate Universe Fics - or at least with the rewritten versions she has begun publishing.
A few of the Expanded Universe authors are known to write under pseudonyms, including Muffin Parcels and A. Sparkler Star.
One of the artists featured on the Breathing Weapons soundtrack goes by the name of, "Satellite Rock". A quick internet search shows this to be the only song by an artist of that name. Given the style of the song, it's widely speculated that the song belongs to the DJ Duo, Blendit/Mixit, but it's still unconfirmed.
Too Soon: Many had this reaction to the description in Purloined Stone of what Discord did to Daring et al.
Similarly, Daring Do and the Cloudfall Conspiracy was first envisioned as a crossover with the Con Mane franchise, but legal and financial issues with the latter's copyright holder prohibited this from happening.
Breathing Weapons was originally intended to be a full spin-off centered around Daring in her later years, her having retired from exploring jungles and ruins and instead doing police work for Celestia. During draft stages, it was deemed too far a departure from the series, and was instead turned into the more traditional (though still quite different) book we have now.
Gospel also claims there was going to be another Greifvogel member by the name of, "Adler", but he was cut because, "there were enough griffons as it was".
Breathing Weapons got released in some regions as, Daring Do and the Industrial Heart for unknown reasons.
In the first few drafts for Iron Grinder, Goblin Grave was originally going to take up Jackhammer's offer to marry Shudder in exchange of giving up his position as pack leader, but Moose realized this would most likely lead to some pretty creepy assumptions by the fans, and as a result, this scene was cut.
There are rumors floating around that the scene where Jackhammer beats Shudder was originally intended to have heavy implications that he had raped her as well, but the writer hasn't said a word about it. Though, recently, a lot of people are claiming this is a rumor started to combat the common portrayal of Rail as a rapist in fanfiction.
The plot of Gunpowder Groove was originally a heavy, realistic take on Zebra racism, with Daring actually casually throwing around the word, "Zigger". Voyage's editor deemed it too serious a topic to tackle, and it was rewritten as a more light-hearted adventure story. Voyage later admitted that this was most likely for the better. Plus, given that Daring's friends with Okpono, who is a zebra, her throwing around language like that would be uncharacteristic.
Gospel claimed she wanted to do a story based on Arzt and his parents finding him after his defection, but her publisher wouldn't allow it due to the fact that it was a Daring Do story that didn't even feature it's main protagonist, and Arzt wasn't as established a character like with the Daren Do Adventures and the Tales of the War series, and was too big for a short story.
Gospel has recently stated that this idea will be explored in the upcoming Globetrotters spin-off.
Some of the early drafts of Amber of the Smooze had the Colt Leader be a Jekhoof and Hide personality of Desert Rose caused by Smooze contac, or an Enemy Without named Tresed. The Colt Leader was later re-imagined as Desert Rose's Bizarro Universe alternate.
Children of Primus is What Could Have Been by itself already, but an even earlier plot outline was recently leaked in which the nature of the titular beings is quite different. According to the source of the leak, the idea was reworked into the more familiar draft because it was decided that the Children of Primus were too powerful, alien, and intimidating to be accepted by potential readers as a rescue team, hence the decision to go with a pair of warring factions instead.
Similarly, Gina Taurus was in talks to voice Nightmare Moon, who would be portrayed via special effects. Then, of course, Princess Luna's big return happened.
Word Of Celestia: Star Shimmer was named after Trotton's wife's cousin, who disappeared under mysterious circumstances years ago.
WTH, Casting Agency?: In the new trailer for the latest adaptation of Alicorn's Shadow, Haystack Leaves has been revealed to play Mareton. Although the stallion's a perfectly good actor, the reaction of many fans was simply, "What." Whether or not he can pull off playing a villain remains to be seen.
Now that another trailer has been released, the general reaction was: "Oh. Right then. Carry on."
Similarly, when Pigroot Cullen was announced as the voice of Optimus Prime in Disneigh's adaptation of Children of Primus, fans were worried that he'd sound too much like Ahuizotl. After actually hearing Cullen's Prime voice in an early trailer, however, they came around.