Why does the stairwell smell so fishy?

Let's investigate, shall we?

Oh, goodness.

Oh my.

Is that...?

A crab?

A TRAIL of crabs? Leading to...

...my neighbor's door?

And around the corner there was this:

A whole mess of crabs, some of them waving their claws in the air in what I presume to be an SOS signal.

Options are:
(1)Someone created this very romantic trail of crabs leading up to my neighbor's door as a belated Valentine's Day gift
(2)Someone is performing an experiment on the effects of crustaceous socialization and gentrification within my apartment building
(3)Anyone got any more? The odor wafting up the stairwell is making it difficult to think. *gag*