WMG / Children's Party at the Palace

The Baddies actually did apologize and reform at the end.

Since they were happy that the Queen got her handbag back and joined in with the Goodies in the "Supercalifragilisticexpialidocious" dance number, they've actually seemed genuinely sincere as if they pulled a Took a Level in Kindness. They made a "fake apology" by offering the Goodies a potion-laced floral cake at first (honestly I'm surprised they didn't make a chocolate cake since Her Majesty is fond of chocolate sweets, after all), but once the handbag was taken back to safety, they admitted that they were meant to sabotage because the story says so and made a genuine apology to the Queen by joining the Goodies with their applause. So it's possible that they made a Heel–Face Turn at the end.

The Queen happens to be a sorceress who used a magic spell or ritual to bring the literature characters to life.

Well, it is possible that she could be a former Hogwarts student (not sure which house though) or a straight up independent mage or practitioner (which would make her implied or assumed to be a closeted Pagan if that's the case, but Christian witches actually do exist). Besides, how could the staff members know that Goodies will be arriving at her party and write up some invitations for them? The Queen must've told them it was a great idea to not only invite the children but also literature characters to entertain them or something, and since people believe that said characters are but fictional, the Queen could've conjured them up into existence somehow. Surely that ritual could've required those characters' respective novels (in physical copy) to be used, so guess the Queen dug them up from the palace library and probably opened to pages where the characters are mentioned. And how the Baddies seem to have a lack of hatred for Her Majesty could be because she's the one who brought them to life, thus earning her their trust. However, Mary and Mr. Tibbs said they won’t be invited so it’s a bit confusing on how the Queen decided to bring the Baddies to life along with the Goodies. But I guess she brought them to life so she could give them a promise that they behave there and become Goodies, and forgot to tell the staff to invite them too. Which they probably did reform at the very end. Wow, she must be very kind.

• That could explain why she's a Big Good and Universally Beloved Leader.

Someone sabotaged Buckingham Palace's security system before Burglar Bill broke in.

Sorry for the sudden Among Us reference but since the Palace would most likely have high quality CCTV cameras and a stronger security system updated after the 1980 break-in of Michael Fagan (heck, it’s actually referenced by Mary), this could be a possibility. The Palace wouldn’t have those grainy grayscale cameras in the mid-2000s and for certain there were security cameras in colour and roughly higher quality footage back in said time period. That camera could've been part of some sort of backup system in case the main system gets tampered with. So maybe another Baddie got in and messed with the other cameras so Burglar Bill won't get easily caught. Not sure which one though since all the Baddies don't seem to care so much about technology let alone have experience in dealing with them.

Burglar Bill was An Impostor.
4 Impostors remain.

The Baddies represent the Seven Deadly Sins.

Oh where to begin.

• Cruella de Vil: Pride. She's very full of herself.
• Grand High Witch: Wrath for sure. She's perhaps the Baddie with the most malicious intents.
• Child-Catcher: Greed, since he catches kids and wants to catch all of them at the party.
• Burglar Bill: He's most likely Greed too since he stole something...important.
• Aunt Sponge: Gluttony. Just look at her.
• Aunt Spiker: Sloth since she is shown sleeping before Burglar Bill arrives with the handbag.
• Captain Hook: Though he shows some shades of Pride, he could be Envy because of his jealousy that his arch-nemesis Peter Pan was invited and not him.
• The Pirate Queen: Probably Lust since she's the only lady of the pirates. And a very feminine one. Maybe all her pirates have fought with each other over which of them will win her heart.
• Technically they all showed envy but it's clear that they all stood out for the other six sins too. That's a clever and subtle detail other people surprisingly haven't pointed out, though it is unclear if it's intentional by the creators of the film.

The Buckingham Palace backdrop is actually an entrance to a secret tunnel that leads to the real Buckingham Palace behind the audience.

There were scenes filmed both on the stage with that backdrop and inside the actual Palace that stands behind the audience watching the stage. And since there’s a scene where the Goodies rush in and try to stop Burglar Bill from behind the props, that area could be where the tunnel starts. Yes, in reality it actually leads to backstage but if the events actually happened this would make sense. Not to mention it would be strange how the Baddies would build their camp in the front of the Palace (that’s what the backdrop showed) without being spotted or trampled over by Royal Guards; it was actually a fake! It would also explain why there appears to be two Buckingham Palaces and how Burglar Bill and the Grand High Witch snuck in that easily.

Cruella de Vil actually likes dogs in this film.

Sure, she may be fantasizing over fur coats, but maybe in this film she's just over-exaggerating at least, and not to mention she fantasized over dogs a lot. Maybe she didn't find the Queen's corgis aggressive towards her, but rather playing too roughly at her feet (which would explain how the corgis were calm already when returning to the stage, let alone not growling or snapping their jaws and that there were so many of them) and was over-exaggerating about their hyperactivity. Rather than trying to skin them, she simply just kept them busy whilst the Baddies crash the party. Her chaperone probably thought she mistreated them when she came back. But that wouldn't explain how she messed up her hair in the process.

The Queen wanted the Baddies to be invited but the Palace staff refused to make invitations for them.

Maybe they assumed the Baddies were too stubborn to take a level in kindness (as evident when Mr. Tibbs said the Baddies have "impulses", not feelings) yet the Queen is optimistic enough to know that everyone, even the villains, have a softer side to their personality and may even change their ways. But because of the staff's incompetence, the Baddies' envy for the Goodies grew on them and they decided to sabotage the party just because they got no invitations. Now the Queen ought to sack them for that, not behead them (despite what Mary said).

The Queen actually had her handbag with her the whole time.

Why else wouldn't she have an extra pair of glasses with her?

• Confirmed, surprisingly. Honestly it would ruin the illusion since her handbag is supposed to be missing, but for sure Her Majesty always brings a spare with her. Well, actually, she does since she got dozens more of those bags in real life but that particular bag she was "supposed to bring with her" had her glasses in it, and not to mention the speech itself.

The potion failed because either the Grand High Witch forgot to add it in the cake or was swapped for something different.

Alright, usually if a potion has the wrong ingredients it would cause a different outcome, not just do nothing. So the most logical reason on how the Goodies did not turn into mice after consuming the cake the Baddies baked is probably because the Grand High Witch forgot to place it in the mix before it was baked, or somebody secretly swapped it for a different liquid without her knowledge: most likely candidates are water, milk, or even buttermilk. It's really interesting how the Baddies spent their time working on the frosting roses though.

The premise of the film is possibly inspired by The Great Yokai War.

As it says, it’s unintentional that the film draws parallels to a Japanese film released a year earlier. But there are some similarities between the two.

• Both films feature lots and lots of characters. As in literature characters and yokai. Heck, the literature characters actually seem a lot like yokai or any mythological creature in general if you think about it, originating from works of fiction and leaking into the real world.
• A party/festival is one of the main settings and is where the antagonists set their base near.
• Both works are examples of Vile Villain, Saccharine Show albeit not reaching into Sugar Bowl levels of saccharine.

Something tells us that one of the creators was probably inspired by The Great Yokai War whilst writing the premise of CPATP, but, of course, sources aren't that abundant on how CPATP came to be besides being a now-obscure pantomime dedicated to both the Queen and British children's literature.

There is going to be a "sequel" of this play in 2022, possibly called “Children’s Platinum Party at the Palace”.

Of course, they haven't said anything about there being a second garden party for the kids with a different play for the Platinum Jubilee but there is a chance they may announce that it's another one of the festivities much later in the year, but it's exclusive to the UK children. Not sure what that play would be about (though one thing for sure is that they're going to a party celebrating the Queen's Platinum Jubilee) or if it's going to feature more literature characters now that more books have been published in the 2010s or just a set from one series.

• One idea, however, is that they should feature mythological creatures from around the world as characters (probably anthropomorphized for the costumes) to represent the impact the Queen has on the entire world. Of course, since not all mythological creatures are benevolent, there would be a couple villains in the mix (some recommendations would be a nekomata, western dragon, and kelpie).
• Unfortunately Jossed. There was no such event during the Platinum Jubilee.

There is going to be a Foreign Remake in America called "Children's Party at the White House" next year.

• Good God, no. Doubt the States have the charisma to make something like what the UK did, let alone copy them.