Mary Bowerman

USA TODAY Network

Despite being known as a burger-giant, during Lent McDonald's has another top-seller: The Filet-O-Fish sandwich.

McDonald's sells nearly 25% of their wild-caught Alaska Pollock fish sandwiches during Lent, when many Catholics forgo meat on Fridays, according to spokeswoman Becca Hary.

The loved and hated Filet-O-Fish sandwich owes its existence on the McDonald's menu to a Cincinnati-franchise owner who noticed in the 1960s that he was losing Catholic customers on Fridays due to the burger-only options.

Filet-O-Fish inventor brought patrons back to McDonald's

Here are five interesting facts about one of the fishiest items on the menu.

1. Lou Groen, who owned the first McDonald's restaurant in Cincinnati, Ohio, came up with the idea of a Filet-O-Fish sandwich in 1962. The people in his neighborhood were predominantly Catholic and during Lent Groen was making next-to-nothing on Fridays, according to McDonald's archivist Mike Bullington. He created a Filet-O-Fish recipe and took it to headquarters, where McDonald's chief Ray Kroc was also preparing his own meatless alternative, Bullington said.

Kroc challenged Groen to a Friday sell-off to see whether customers preferred Kroc's Hula Burger, which consisted of a piece of grilled pineapple and cheese on a bun, or the Filet-O-Fish. Bullington said Groen won by a landslide, with the Hula Burger selling six sandwiches and Filet-O-Fish selling 350.

2. Welcome to the permanent menu. In 1965, the Filet-O-Fish sandwich became the only non-hamburger menu item. A sandwich only cost $0.29. Sandwiches for everyone!

3. The Filet-O-Fish isn't just a popular item in the U.S. The sandwich is now served overseas in countries like Russia, Japan and India.

4. There's a wasabi version of the sandwich in Asia, and in the U.S., select McDonald's carry an Old Bay Filet-O-Fish.

5. Believe it or not, the Filet-O-Fish is actually fish. McDonald's uses Marine Stewardship Council certified wild-caught Alaska Pollock.

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