Prepare jalapeno, onion, and garlic, then add to Slow Cooker or Instant Pot.
Add cumin, oregano, chili powder, black pepper, and salt to a bowl and mix to combine. Coat the pork shoulder with the seasoning.
Add pork shoulder and Dr. Pepper. Slow cook on high for 6 hours, low for 8 hours. In Instant Pot, Slow Cook on Normal for 8 hours, More for 7 ½ hours.
Remove lid once cooking time is up. Shred the pork in the liquid before removing it. Fish out the shredded pork and put in a sieve or spider to remove excess liquid.
Heat 2 tablespoons of bacon grease in skillet over medium heat. Once heated, arrange shredded pork in an even layer in the pan and cook, uncovered, for 4-5 minutes.
Using tongs, flip the pork. It should appear golden brown and crispy. Continue cooking for another 3-4 minutes.
Remove from heat and serve hot! These Crispy Slow Cooked Dr. Pepper Carnitas make fantastic tacos, burritos, and quesadillas