Cut onion in slices and line the bottom of the crockpot. Lay the pork shoulder on top. Sprinkle pork with brown sugar and salt and pepper.
Pour the can of chipotle peppers on top of the pork and pour both cans of Dr Pepper on top.
Turn the crockpot on low and cook for 4-6 hours. Remove pork from the slow cooker and shred. I also took the chipotle peppers out so they weren’t too hot for the little ones. Return the shredded pork to crockpot and allow to heat through.
Serve on tortillas and top with favorite toppings.