Theme Days

While not universally followed throughout the 4chan population, certain themes are flooded during the different days of the week by some factions. Many of the themes are /b/-only material.
 * Miko-Maid Monday
 * Warhammer Wednesday
 * Furry Friday
 * Caturday (or Cat Saturday to those missing chromosomes)
 * Scaturday or Faturday are sometimes seen, with pictures of fat people and BBW models
 * Bunday, with pictures of bunnies
 * Guro Sunday, for the freaks.

On some boards, even more specialized theme days crop up, typically relating to an anime/manga/game or a specific character whose name is at least vaguely similar to the day's name. For example, on /e/ and /h/, Friday is often "Riday", with images of Rider from Fate/stay night being flooded.

An ongoing joke is that despite these themes, every day is Repost Day.

Every day is Repost Day.
Response to source requests of an image that is reposted frequently, often to the point that no one knows where it came from prior to arriving at 4chan. Sometimes seen as "Source is 4chan. Every day is Repost Day."

Every repost is repost repost.
A derivative of "Every day is Repost Day."

Source is 4chan.

 * See: Every day is Repost Day.