As of this week, more than 20,000 TEDxTalks have been given at 5,000+ events held in 137 countries around the globe. With the mass scale of the program, it’s a little unpredictable which talks will gain a steady following of fans on the TEDxTalks website and YouTube channel, and which talks will skyrocket into public consciousness practically overnight. Below, six TEDxTalks that became phenomena and had ripple effects their speakers hardly could have anticipated.

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Brené Brown: The power of vulnerability
Brené Brown has inspired millions to embrace their vulnerability, with one of the most forthright and deeply personal presentations ever featured on TED. When Brown first gave her talk at TEDxHouston, she had no idea that — just two years later — nearly 5 million people would have watched it. “I call 2010 the year of the vulnerability talk and 2011 the year of walking the talk, because I was very unprepared,” Brown told the TED Blog before the posting of her second talk, “Listening to shame” at TED2012.

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Thomas Suarez: A 12-year-old app developer
At TEDxManhattanBeach in 2011, Thomas Suarez showed the world what growing up digital can do to kids: turn them into engineers. When he gave his talk, Suarez had already developed a widely circulated iPhone whack-a-mole app called “Bustin Jeiber,” and had started tutoring other kids to become developers too. His talk has made more than a million TED viewers feel excessively guilty about what they were doing at age 12.

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Larry Smith: Why you will fail to have a great career
Few can tell it like it is quite the way Larry Smith can. This extremely popular talk, given at TEDxUW in 2011, holds an outlandish paradox: Smith’s observations about your future are pessimistic and his tone nearly apoplectic, and yet he leaves you feeling richly inspired to take control of your life’s path. More than 1.2 million people have enjoyed this talk as a result.

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Joe Smith: How to use a paper towel
Most people probably assumed they knew how to use a paper towel before Joe Smith gave a talk on the subject at TEDxConcordiaUPortland. But with the simplest of choreography — shake and fold — he transformed how millions of people dry their hands. It’s easy to spot those who have seen Smith’s talk by the way they leave a public bathroom, and TED staffers are happy to see his technique spreading rapidly.

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Dan Meyer: Math class needs a makeover
Dan Meyer is evangelist for making math fun. By sharing his methods for engaging students with real problem solving at TEDxNYED, his talk has pushed forward a radical shift in the way we educate our kids. Nearly a million people have seen the talk so far — many of them teachers — kick starting something of a math revolution.

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Ami Klin: A new way to diagnose autism
It doesn’t always take a million views for a TEDxTalk to make an impact. Perhaps by coincidence, just four months after we posted Ami Klin’s talk from TEDxPeachtree about his urgent research into early childhood autism, the NIH granted his team $8.3 million to create a new Autism Center of Excellence — one of only three in the United States.

Stay tuned to the TED Blog all this week for a celebration of TEDx or, if you’re curious, check out the TEDx blog.