Pop Badges started "Popping Up" at Legoland Parks around 2008 presumably as a lower cost alternative to Promo Bricks for Annual Passholders, smaller events / achievements that didn't necessarily warrant a Promo Brick, or even as a secondary reward for larger events like Brick or Treat where a Promo Brick was released.

I do not believe Merlin or Lego actually invented the Pop Badge but they do utilize them at nearly all of their Legoland Parks. 

Many badges do not specify the actual Park location just the Event ,Season or Holiday enabling them to use the same badges at multiple Parks

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"Pop Badges introduce a whole new adventure to the LEGOLAND experience. A Pop Badge is exactly that… a badge that pops right on to a lanyard or shirt, so you can proudly wear them once you collect them!"

- Legoland