The first time this happened to me, there was no sign. Please don’t underestimate the sound, vibration, and fury of this “huge rattling.” I was certain one of the following  scenarios was occurring:

1) My worst childhood fear is coming true– Jaws has found a way to exist in the toilet, and the flush is his attack signal.

2) Zombie apocalypse: attack of the pipe people.

3) I’m hallucinating. Things like this don’t happen to educated professionals at their place of employment. Did I take my meds today?

4) This “bathroom” is, as I’ve always suspected, a torture chamber for serial killers, designed to implode after any sudden movements.

5) I’ve done it. I’ve angered God.

But no. Turns out we just work in a dilapidated shithole that probably once housed zoo animals.

So…phew?