As the flavor text suggests, each thirteen-letter word is made up of thirteen different letters, one taken from each row. The best way to attack this is to look for prefixes (UN-) and suffixes (-ING, -LY) and then narrow things down from there. The remaining words are:

UNPREDICTABLY

UNPROBLEMATIC

TROUBLEMAKING

MOTHERFUCKING (now you see why we needed the PG-13 rating!)

COPYRIGHTABLE

The letters in the bolded boxes spell out LYCANTHROPIES, a Halloween-themed word (however awkward!) that fits the same pattern.