It's actually a giant, inter-dimentional conspiracy.
Ponies use their cuteness to induce heart-attacks in most of the population, thus paving the way for their eventual invasion.
I've been forming a small resistance movement to try to stop-
*ding-dong
The door?
Yes, what do you want?

NOOOOOOOOO!
HNNNNGGGGG-

You can't stop them. No one can. It was already to late when they started to do it.