Okay, wow. I loved this. Setting the mission within the actual medium of stage performance is clever and fun, and I especially loved the "subtitles" when the agents were trying to mime information to each other. The ending scene, where the canon and PPC characters all celebrate together, is rather sweet, and it's a unique and medium-appropriate way for canon to return after the Suvian influence ends. All in all, a perfect way to wrap up this little arc of the four getting stuck in RC hook'em horns together!

One important note, though: Urato drops f-bombs a few times in here, but you didn't warn for language in either the Board post or the author's note. We don't want our younger members getting in trouble with parents or teachers reading over their shoulders, so please make sure to do so!

Typos:
" . . . Inasuke thought, switching off the overheating CAD and hoped it wouldn't turn itself back on again."
"Hoped" should be "hoping" to match the same verb tense as "switching off." (Alternatively, "CAD; he hoped" would fit there too, but that's changing a lot more from your original sentence.)

"It felt as though every of his muscle fibers was being torn apart . . ."
This is a weird quirk of English, and I don't think I have any academic way of explaining it, but using "every" like this needs to have "one" after: "every one of his muscles." "Each" can be substituted by itself, "each of his muscles," but I don't think that really works here. It sounds a little too clinical in this context.

—doctorlit doesn't really listen to classical, but he knew two of the songs named here! ("Danse" and "Valkyries.")

I thought the mission was pretty good—seriously, that was an odd Sue. And in a new (to the PPC) canon, too!

I didn’t understand the Japanese, but I don’t speak Japanese. No surprise there.

I think I saw an error:

“The other agents didn't have it any easier, as they didn't have much room to move yet under threat of a Sue feet's falling on their heads:”

The “a Sue’s feet” is difficult to parse, it’d be better phrased as “one of the Sue’s feet”.

Can I have Drosselmeier, please?

(Side note: what would a misspelled Mini be?)

Anyway, good job!

Also, there are some things I would like to point out. I'm not mad.

"Alas, how his and his mini Booky held their breaths at the battle against the mouse king!"

I assume you mean "Alas, how he and his mini, Booky, held their breaths?"

It was amazing how fast Urato grew from ambivalent towards to totally loathing a piece of music; if he heard that annoying celesta melody to Sugar Plum Fairy just one more time, there was a high chance something would end up horribly broken.

This is a very long sentence, and I think it reads more like two sentences stuck together.

The CAD reading on Stephanie made me laugh. I'm wondering the same thing. I will post more when I have time.