Nearly 25 percent of the sandwiches sold during the year are sold during Lent, which begins on Ash Wednesday and runs for 40 days, ending just before Easter Sunday.
The dish’s existence dates back to the 1960s, when Cincinnati franchise owner Lou Groen noticed a drop in sales on Fridays when his Roman Catholic customers were observing Lent.
Groen convinced the food chain to launch a whitefish sandwich as an alternative menu item to its popular burgers.
Since its inception, the wild-caught Alaska pollock fish sandwiches have become a McDonald’s staple.
Social media users are jokingly taking to Twitter to express their excitement for “Filet-O-Fish Season,” some celebrating the discounts that many McDonald’s restaurants offer on the sandwich on Fridays during Lent.