The New York Yankees completed their ALDS comeback and beat the Indians in Game 5 (NYY 5, CLE 2) on Wednesday night to advance to the ALCS, where they will take on the Houston Astros. That series begins Friday night in Houston. Here's everything you need to know about the ALCS.

If you watched the ALDS at all -- and I hope you did, it was a very exciting series -- chances are you saw the Yankees giving each other the thumbs down after a base hit. For example, here is Starlin Castro following a hit in Game 4 of the ALDS on Monday:

MLB: ALDS-Cleveland Indians at New York Yankees
The thumbs down is taking over New York baseball. USATSI

Teams around the league have come up with extravagant hand signals after a base hit for years now. Remember the 2010-11 Rangers and their antlers? That kind of started the whole fad. Now it's widespread and pretty much every team in MLB does it. It's fun. It's harmless.

But a thumbs down? That's a little usual. A thumbs up is good, a thumbs down is bad. This all dates back to a home run by Todd Frazier on Sept. 11, during a neutral site game at Citi Field against the Rays. The game was a Rays home game moved there because of Hurricane Irma. Here's the home run:

During the YES Network broadcast, the cameras found a Mets fan in the stands giving Frazier a big ol' thumbs down for the home run. Someone showed Frazier the clip on social media, and he decided to adopt it as his own way to celebrate a base hit. He first did it two days later:

Since then, the thumbs down has taken on a life of its own. It has spread throughout the team and now every Yankee, after a base hit, turns around and gives the dugout a thumbs down. And the dugout gives the thumbs down right back:

The Yankees had a big September and qualified for the postseason, and the thumbs down kept coming. They have shirts and everything now. Check it out:

And of course fans have bought in as well. Thumbs down is officially A Thing:

Cheesy? Yeah, maybe. Don't like it? Too bad. The Yankees are very good and there are a lot of thumbs down going around. Their fans are eating it up. This is the rallying cry of the 2017 Yankees. A thumbs down started by a Mets fan not happy Frazier hit a home run in their ballpark. Inspiration comes from the weirdest places.