St Paddy’s Day is no doubt a day full of drinking… Guinness, Jameson, Bailey’s, and, for all of those that aren’t 21 yet, let’s not forget about the seasonal Shamrock Shakes from McDonald’s. Here are 12 things you might not know about the minty holiday favorite.

1. They were first introduced in the United States in 1970

Shamrock Shakes

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Since then, McDonald’s has sold over 60 million Shamrock Shakes.

2. A giant Shamrock Shake is made each year for the Chicago St. Patrick’s Day celebration

Shamrock Shakes

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Each year, the Chicago River is dyed green for St. Patrick’s day. In 2010, advertising executive Leo Burnett created a giant Shamrock Shake cup that he tipped over to make it look like it was pouring into the river — they’ve done it every year since.

3. Shamrock Shakes contributed to funding the first ever Ronald McDonald House

Shamrock Shakes

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In 1974, Philadelphia Eagles’ tight end Fred Hill had a daughter fighting leukemia, so he wanted to create a place where families could stay if they were in a similar situation. He was seeing firsthand how families were being affected, and wanted to establish a sense of home away from home.

McDonald’s donated a portion of the profit from Shamrock Shake sales to the project, in exchange for being able to name the new house. They were able to purchase an old 7-bedroom house that became the first ever Ronald McDonald House. Today there are over 350 similar houses worldwide.

4. In 1978, McDonald’s introduced Uncle O’Grimacey as the face of Shamrock Shakes

He was the Irish uncle of Grimace, the McDonaldland character, but he was phased out of advertising in the early ’80s.

5. ShamrockShake.com is totally a thing

Shamrock Shakes

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If you’re wondering where you can find one of these seasonal shakes, you can check out this website to see where people have reported buying them. Have they made it to your town yet?

6. They are really, really bad for you — but we don’t care

Shamrock Shakes

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A large Shamrock Shake has about 820 calories. That is the equivalent of 1.25 Big Macs, 1.5 large fries, 2.5 Sundaes, or 3 Egg McMuffins. Yolo.

7. In 2011, Jimmy Fallon wiped out the Union Square McDonald’s supply of Shamrock Shakes

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He bought one for everyone in his crew and his studio audience.

8. Shamrock Shakes were completely discontinued in the ’90s

Shamrock Shakes

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Thankfully, due to a huge internet revolution, they were brought back in the 2000s.

9. McDonald’s introduced a Shamrock Sundae in 1980

Shamrock Shakes

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It was a huge flop and it didn’t sell, to the point that it was discontinued in a year.

10. 2012 was the first year that Shamrock Shakes were available worldwide

Shamrock Shakes

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However, regional managers make the decision on whether or not their store will carry them.

11. They were originally called the super creative and catchy “St. Patrick’s Day Green Milkshake

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Simply mouthwatering.

12. There is a chocolate version of the Shamrock Shake called the “McLeprechaun Shake

Shamrock Shakes

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YES PLEASE.