Suite Pretty Cure/WMG

Hummy may become able to transform into a human later on.

 * Siren can do the same, so why not?
 * Jossed (Or is it?). But only time will tell.

Siren helps two other girls transform into evil Cures.

 * Jossed

Mephisto is a Disc One Final Boss.

 * Gawd, I hope so...please be true.
 * Very likely. If you look closely at him in some shots, you'll notice he's wearing the same brainwashing devices he used on Siren.
 * Though, he apparently uses them for all manner of things, including powering up his minions, so who knows? They may just be a fashion statement.
 * Events in Episodes 29 and 30 seem to point in this direction.

Siren is going to pull a Heel Face Turn.

 * She's a fairy with a cute human form who used to be on the side of good and has the potential for a sympathetic backstory. It wouldn't be implausible. Since she's important to the villains, there's a good chance that if this happens, it won't be until very late in the series.
 * They certainly seem to be showing hints of this in Episode 8. I just hope it doesn't mean the Minor Trio become more prominent in the series. I cringe every time they start to sing.
 * Confirmed; she turns face after episode 21 and becomes Cure Beat in episode 22.

Three of the Fairy Tones are for other Precure.

 * The remaining two will be used for team attacks or alternate forms.

Kanade yelling Hibiki's name will be a Once an Episode thing.

 * Jossed: the Once an Episode thing is the Cures shouting "This Is Unforgivable!" before everytime they transform.

The true identity of Cure Muse is Siren.

 * Although it may not be the case since Siren has Eyes of Gold while Cure Muse's eyes are pink.
 * Shapeshifting, remember? She already use two separate human forms from Ellen.
 * But Youko Yamaguchi and Sakura were only used once. Ellen is her standard human form, and even then her eyes are yellow.
 * Doesn't mean she can't make a separate form for Cure Muse, or maybe just change the eyes
 * Appears to be Jossed; the two characters showed up in the same scene in episode 13.
 * Also played with as in the next episode Siren pretended to be Muse, even with the eyes. The only difference was Siren's tag remained while as Cure Muse.
 * Officially Jossed.

The true identity of Cure Muse is Cure

 * Jossed

The true identity of Cure Muse is Cure Beat

 * Hey, anything can happen in these WMGs!
 * "It would be like Sailor V from Sailor Moon before she was Sailor Venus," noting that Suite Pretty Cure and Sailor Moon have many of the same production staff members
 * Jossed; Cure Beat is Siren.

The true identity of Cure Muse is Ako

 * Well, it seems like she's an important character... This is why Muse is The Voiceless: Dodori does all the talking to cover up the fact that Muse still sounds like the much-younger Ako, kind of like how the Byakkoshinken initially spoke for Kibaranger. However, there is a major problem with this theory: no other Cures have their eye color change when transformed, and Muse's eyes are an entirely different color than Ako's.
 * No other Cure had a Older Alter Ego either, let alone a Cure costume like Muse's. It could either be part of the magic (like how the Cures get different hair color in recent seasons. Keep in mind, the first season, the Cures didn't change hairstyle either) or something mundane, like she wears eye contacts or part of the mask's, as if they were realistic looking lenses.
 * So far, Ako and Muse have not been seen at the same time. Also,  Could be a coincidence, but it certainly is suspicious.

Suite takes place in the same universe as Yes Pretty Cure 5, but in the future...
...And Rin is Hibiki's paternal grandmother, hence why Hibiki likes soccer so much and why her father Dan looks so much like Rin. Well, everyone knows that the Pretty Cure All Stars movies aren't canon, so...

Alternately, if you're in the crowd that considers the All-Stars movies canon, it could be said that Rin's mother Kazuyo is Dan's widowed sister (Rin's father probably died prior to the start of the series, as he was never seen onscreen during YPC5's run and Kazuyo keeps her married surname instead of switching back to her maiden one thus discarding a divorce possibility), thus making Rin and Hibiki cousins. Either way, the Fiery Redhead soccer loving tomboy gene is probably In the Blood.

There will more Pretty Cures

 * Confirmed by now, if you think about Cures Beat and Muse...

The true identity of Cure Muse is Hummy

 * Hey, anything can happen in these WMGs!
 * Jossed;

The true identity of Cure Muse is Aphrodite

 * The oft-repeated 'goddess of music' is actually Foreshadowing.
 * Jossed

Theory about Hibiki's sexuality
That's a bit of a stretch, but she's the only girl in Aria Private Academy that doesn't crush on Ouji, who appears to be so handsome no straight girl can resist him. With that, it could be only said that...
 * She's not attracted to boys at all, making her a Chapstick Lesbian. That, or she's secretly Kanade-sexual.
 * Alternately, she could have a secret fetish for guys who are ugly, freaky, or simply don't fit the preestablished beauty standards.
 * Or she could be asexual.
 * Or she could be more interested in the bad boy type, which Aria Private Academy seems to lack.

Otokichi is Aphrodite's father or grandfather.
He's been helping the Precure on a few different occasions now, most recently (at the time of this writing) playing a song that not only saved them from a Negatone, but also caused Seiren to comment on the power she sensed from the person playing. His work on the pipe organ also seems to be tied to the melody of happiness, as the notes were drawn to the sound of it. His eye color is similar to that of Aphrodite, and his overall look seems to be more like someone from Major Land than someone from earth.
 * This would make Ako Aphrodite's daughter, or the very least her niece.

Hummy's place in the second Ending will be replaced by Cure Muse after her identity is revealed.
Given the camera angles used in the sequence, it looks like they set it up so they just have to replace Hummy's model with the new cure and re-render it. Hummy's even riding on a Yellow platform at one point, a color that has been linked to the likely 4th Cure (not counting Muse as she currently appears).
 * More or less confirmed with the revamped ending introduced with Episode 38. Many of the shots that featured Hummy previously have been swapped out for Cure Muse. Hummy is still present, but in a much less prominent way.

Siren's High Heel Face Turn ruined the bad guys plans, they just haven't realized it yet.
They could probably find a replacement or sing themselves.

Grand Unifying Theory: Mephisto and Aphrodite are husband and wife.
It's a pseudo-redux of the relationship between the Dark King and the Queen of Light. At some point in the past, Major Land and Minor Land were united into a single kingdom with Mephisto and Aphrodite ruling over it. At some point, Mephisto came into contact with the Noise of Evil -- a power source with known brainwashing capabilities, whose emitters he can be seen wearing over his ears in some scenes -- and the kingdom split after he fell under the influence of this season's Eldritch Abomination. Hence why he seems relatively harmless compared to past Big Bads, there's a Man Behind the Man pulling his strings. This falling out between the king and queen -- similar to a divorce in the effect it has on the family, especially the kids -- resulted in the daughter of the two rulers, one Ako Shirabe (most likely an assumed name), turning into a jaded and cynical Rebellious Princess and running away to Earth, where she takes up the mantle of Cure Muse, using stronger-than-normal disguise magic to conceal her age in order to hide from everyone, especially her parents. This is why she says she's not on anyone's side, that would entail siding with one of her parents when she's rebelling against both of them. Otokichi is Ako's grandfather -- probably on Mephisto's side because he refers to having a son early in the season -- and is hanging around to keep an eye on her.
 * Episode 30 adds credence to the Brainwashed Mephisto part, with hints at Otokichi's ties to Major Land.
 * Episode 29 suggests how it may have happened, since Mephisto alludes to having been to the Forest of Evil before and the force infesting the forest tries to use the Noise of Evil against the Cures.
 * Episode 35 reveals that.
 * Episode 36 reveals that

Kanade was supposed to be a green-clad Cure, but was unfortunately changed to white and pink before the designs were leaked.
They probably changed it, either because they thought pink and green wouldn't make a good couple, or to, much like they said in an early advert, "put girls' favorite color (pink) on display". When you think about it, there are many hints splattered around for this.
 * Her childhood flashback clothes are green.
 * Her summer dress is sea green.
 * The podium she stands on during the second Ending Theme is a very light sea green.
 * Episodes 26, 28 and 30 have scenes with a Super Deformed version of Kanade represented by sea green outlines.
 * That may be a bit of a stretch, but this may be the reason for her eyes being green as well.

The voice Hibiki keeps hearing isn't real.
She is simply experiencing auditory hallucinations.
 * Jossed; the voice belongs to the Crescendo Fairy Tone, therefore it is real.

Cure Muse is Ako from an alternate future.
A few years from now, in an alternate timeline, Mephisto rules all three worlds after the defeat of Cures Melody and Rhythm at the hands of Trio the Minor. Ako, who is one of the only people left who have not succumbed to the Melody of Sorrow, becomes a Precure to combat the forces of Minor Land. She discovers a way to travel back in time to assist Melody and Rhythm, hoping to Set Right What Once Went Wrong. She takes on the guise of Cure Muse in order to not interfere too much with her own past self.
 * Obviously, this theory is dependent on Muse being Ako in the first place.
 * The Crescendo Tone appears to be aware of her mission, recognizing Muse's desire to protect the other Cures.
 * One possible reason why
 * Jossed;

The season will end in a cliffhanger, and The Movie will be the finale.

 * Jossed.