"So," Twilight began, "care to explain why my castle is on fire?"
"I just don't know what went wrong!" Derby exclaimed, ash coating her fur.
"I do, though," Berry Punch said forlornly. "It all started when Shining Armor got a bit too drunk in my shop. Next thing we knew, there was a giant party going on here at the castle. I guess he's staying in town for something?"
"Yeah, I have a conference on defense shield spellcasting techniques scheduled for this weekend. But why the fuck is my castle on fire?"
"Well, you know how Derpy has bubbles as her cutie mark? Well it turns out those are bubbles of hydrogen gas. And she is constantly emitting hydrogen gas. It's weird--I don't know how she does it. But that's just one of the things that makes her my lovely dovey shmoopy whoopy doopy Derpy Do!"
"Wait, are you saying that her ass combusted or something?"
"I mean she does have a hot ass, but no. Shining Armor was going to do that trick were like you jump through a mirror into a human world and then steal a $100 bill and then use alcohol to set the bill on fire except it's not really on fire."
"Wait a minute, ponies are using my magic mirror without my permission? Unacceptable!"
"Anyway, the fiery bill lit Derpy's ass on fire, and that's how Equestria was made."
Twilight sighed. "So did you guys ever consider trying to put the fire out?"
"We did, but it just kept burning. It turns out Derpy's ass is just too hot."
"You really have a thing for Derby's ass don't you?"
"I mean really, who doesn't? We call her bubble butt for a reason."
"Say, I have an idea, being smart and all that," said Twilight. "Since Derpy has such a fat ass, why doesn't she sit on my castle, starving the fire of oxygen and smothering it! That should work, right?"
"No, remember, her ass exudes hydrogen? She'd go up like a rocket ship.
"Darn. What if we wrapped it in bubble wrap?"
"I mean that could work. Given her job as a delivery pony, she probably has bubble wrap."
Suddenly, Derpy reentered the conversation. "Hey guys, I put the fire out!"
Twilight and Berry spoke in unison: "How?!"
"Well, as you know, I'm great at shipping things. So I shipped your castle with the Ponyville Lake. They're my OTP. The castle is a bit soggy now, but the fire is out!
"Dammit, Derpy."