It's Starlight Glimmer1's fault.

"Spike?" Twilight groaned, pushing the debris away from her bruised body. "Spike? Did you check before you knocked down that wall that it wasn't a weight-supporting structure?"

"An--" a voice gasped somewhere to the side. "An alicorn? B-but where's Sunny?"

"Aw sht, here we go again..." Twilight muttered.

"Magic!" Sunny gaped at the sight of Spike's panicked dragonfire. "And a little dragon!"

Spike turned around, fear evident in his eyes. "Oooh no. Oh boy, I messed up hard this time, didn't I?"

"Twilight, darling--" Rarity opened the door, only to find Sunny staring at Spike. "--I... will... come back later. I see that you're quite busy."

"WAIT DID YOU JUST USE MAGIC TO OPEN THE DOO--"