Spike's claws made muffled thumping sounds as he paced impatiently up and down the hallway of his and Twilight's apartment over the Golden Oaks Library. As time went on, his pacing became more and more urgent, and he started whining to himself. It finally got to the point where he could no longer stand to wait for another second, so he clomped right up to the bathroom door and banged on it.
"Twilight, come on! I have to go to the bathroom!" he shouted.
The only response from the other side was an incoherent groan that sounded like, "Ahhhhhhhhh yeah... Ooohh..." This concerned Spike, because Twilight usually made sense even when she was talking about science or other gibberish, and he knew she wasn't getting a massage because Rarity had once mentioned (in anguish) that the spa mares didn't do house calls. So, Spike did the only logical thing a dragon could do in such a situation, which certainly was not asking if she was alright.
"I'm coming in!" Apparently, Twilight had forgotten to lock the door, so Spike was able to open it without having to knock it down.
What he found when he burst into the room was the following scene: Twilight Sparkle sitting on the toilet with one hoof on her horn and a magazine floating in front of her. Naturally, Spike understood exactly what was going on, having been caught in similar positions several times by the unicorn. He immediately started backpeddling towards the door.
"Spike," Twilight began, "please knock next t--"
"I'm so sorry I didn't know you were masturbating don't give me extra chores I'll go over to Pipsqueak's house and use his toilet I'm so sorry don't punish me I didn't know and that isn't my Playcolt magazine 'cause I don't keep that in the b--I mean I don't have one of those you can't prove I do--" Spike's apologies continued even as he fled down the stairs.
"Hum, I wonder what that was all about," said Twilight, who hadn't understood half of his frantic rambling.
She finished brushing the stray filings off her horn and picked up the file with her magic. Soon, she'd immersed herself in the article about foreign library cataloguing systems again, occasionally shivering and muttering, "Ooh, yeah," when the file massaged a particularly sore spot.