A flood of furry hentai that occurs every Friday on the random (/b/) section of 4chan. Of course, now with the word filter, one is unable to say the phrase "furry friday" in /b/. (If you try to type 'furry', it is replaced with the word drama) Many users contribute to furry friday throughout multiple threads. Usually, one furry thread on furry friday will be followed up with 30 or so text replies and 15 or so furry pics.
If you don't like furry (I sure as hell do), don't go to 4chan's /b/ on furry friday.