I laughed at words! I don't do that very often! Good job!

And I don't even know anything about this continuum.

The butter side down test made me laugh, and the remarks about clocks in PPC HQ made me giggle. I can't remember having ever said this about other missions; they mostly just make me smile.

BTW I smiled a lot here; Ix already covered that.

Of course I deliver:

She cleans up real nice ...
I believe this should be "really nice", but I'm not a native speaker and may be wrong.

[Present tense detected.  Revert agents to to permanent past tense Y/N?]
Repetition.

Sean quickly threw the CAD as far as he can. 
I'm not sure whether this is intentional. Considering that Sean is probably still able to throw a CAD as far as he could then, it may be a stylistic choice. (Like the high-heeled shoes that so many World One women wear, which didn't stick out as odd to me. I actually like that you apparently don't believe that, since the narration is in past tense, everything must be in past tense.)

He just wouldn’t be be having four days of non-stop woobified wangst in the first place.
Repetition.

Hild shudders.
Tense shift.

HG

I really don't have much to say in the way of concrit or SPaG-picking (though I'm willing to bet HG will spot something, he always does), so I'm just going to do a sort of "Ix Reacts".

“Anyway, for your information, a bunch of agents are organising evening classes. They think it’ll help keep us sane, or something. And Lux is teaching one of the courses.”
*head tilt* Do I even want to know?

Hild shook her head. “It’s taxidermy.
Ohhh, okay. Neat.

[Jeeves. Human. OOC 43% so far, and increasing. As he’s the second person narrator, I bet he’ll turn out to be a possible Replacement Stu. Did you really need me to tell you that?]

Sean briefly wished his CAD would just explode like so many others.
*snorts* Okay, that was pretty funny.

[Bertie Wooster. Human. OOC at least 100%, possibly more, and increasing. Replacement Woobie!Stu-stu-studio, Studio Line! Central line! District line! Northern line descended from Valandil! Valerie Singleton! Valley of Death! Welcome to Death Valley Days! The driver is either dead or missing!]

Sean quickly threw the CAD as far as he can. It sailed over the cliff and then finally exploded.
*cacklesnorts* Okay, that's pretty funny.

As Jeeves hugged Bertie and led him away from the cliff, Hild stopped merely twitching her shoulders, and started reaching round to feel them then twisting her head trying to look at her back.

“Hild! What is the matter with you?”

She glanced sheepishly at him. “I was just trying to flap my wings.”

“Wings?” Sean’s brow furrowed, before comprehension spread across his face. “I know you’re a flapper, but it doesn’t mean anything. It’s just a name for how you’re dressed.”

“So there’s – there’s nothing to actually flap?”

“’Fraid not.”
Pffff, poor Hild.

“Yes, but what is a bicycle ride?”
Yeah, is this some sort of metaphor that's gone sailing over my head, or is it a reference?

Just then, a flapping noise was heard above the roaring of the flames. The agents looked up to see a large zero flying around their heads, with tildes for wings.

“Now that’s what I call a flapper!”
Okay, that's pretty funny--

“It’s a scene divider. Grab it!” said Sean. He and Hild managed to catch hold of the bottom of the flying zero, and were lifted up.
O__O SO COOL. Okay, I like this idea. That is awesome.

Hild giggled. “OK. Now, since you’re in the mood for explanations, what is a bicycle ride?”

Sean attempted to explain. It was a difficult business, not helped by having to duck down behind the sofa again as Jeeves carried a plate of toast to Bertie’s bedroom.

“Thanks,” Hild said when the explanation was over.
... :/

Sean leant over to look at it. “Hmmm... Butter side up.” He picked the toast up. “This universe is more messed up than we realised.”
*spits milk everywhere* AHAHA, YES!

Later:
“Hey, it’s not our fault if the fic’s mistakes cancelled each other out.” He dropped the toast to prove his point. It did indeed land butter side down.
OMG YOU DID THAT YOU REALLY DID THAT

So, in conclusion, I enjoyed this. A lot. Good work! :)

What I want to know is what Sean meant with the cliff joke, as I'm not a Brit.