Because I felt like it

Paradoxical Animaniacs

"Idris wait!" The Doctor yelled. "Ten is here!" The TARDIS paid him no mind. "-you look very much alike." Came from the inside of the building.

The Doctor found Idris hiding behind... well, herself. Her past self anyways. Idris had snuck inside and dashed behind Ten's TARDIS.

"Shh, I know what I'm doing." Idris whispered. "Plus, I wanted to see all three of you here!"

"Well I guess if you planned-wait, what do you mean all three?!" The Doctor's concerns went unnoticed by Idris.

Then, Eleven noticed the girl who wanted to become a prophet about to inhale the smoke... Which would wind up killing her!

"Stop! That's alien dust!!!" Eleven cried, abandoning his hiding space. Both TARDISes face palmed.

"What- Eleven?!" Ten exclaimed.

"Ten!" Eleven shouted.

"Wh-what are you doing here?!" Ten stammered.

"I'm not sure, it was the TARDIS's idea, and my new companions as well, of course!" Eleven explained.

"But you shouldn't be here! We're the same person, what if it causes a paradox." Ten protested.

"Shut up. It won't cause a paradox, I'm already here." Both Doctors turned to the roman man, confused.

"What? You-what? What?!" They asked in synch.

"Honestly, look, I'm Twelve!" He snapped.

The three Doctors started to argue, trying to clear their confusion.

"Wonderful. All I wanted was to have a chat with Twelve." Idris groaned.

"Hold up, what's going on?" One of the Romans asked.

"Ah, yes, mini-me. I'll explain later." Twelve said, talking to his "son".

They didn't get a chance to ask any more questions because the "fireplace" blew up.

"It's the creature from the prophecy!" The girl shouted.

"No, it's an evil alien from outer space!" The Doctors corrected.

Just then, Eleven's two companions rushed in.

"We heard an explosion!" Loki announced.

"Is something on fire?" Adan asked innocently.

"Oi! Who are they?!" Donna demanded.

"Those would be my companions." Eleven announced.

"Oh, not them again." Twelve complained quietly.

"Should we focus on the large angry stone fellow right there?" Adan wondered.

No one listened to him and continued squabbling until the alien smashed its fists into the ground, shattering the expensive floor.

"It took forever to get that installed..." Twelve pouted.

"I've got it!" Adan shouted, drawing the alien's attention. It roared furiously, and failed to impress the dragon at all.

Adan raised an eyebrow before holding up his hand, siphoning the intense heat from the magma coated being, freezing it instantly.

"What? How did you do that?!" Eleven shouted.

Adan shrugged. "It's the same idea as breathing fire. It wasn't hard."

Then the alien exploded into tiny little pieces.

"Why did that happen?" Loki wondered.

"There's three Doctors and one house, the Time Stream can't handle it." Idris explained.