In a small bowl combine all the rub ingredients together to form a thick slurry.
Place pork butt in the crockpot and smother with the spice slurry.
Sprinkle the rough chopped onion, jalapeno and bay leaves over and around the pork. Pour the orange and lime juices into the crockpot, trying not to wash the spice rub off of the pork! Cover and cook on low for 9-10 hours. If you don't have quite that much time you can cook on hi for 6-7 hours.
Once the pork is super tender (you should be able stick a fork into the meat very easily, hence the term fork tender!) carefully lift it out of the crockpot and onto a large cutting board, preferably one with a drip ring around it to catch the juices. Using two forks, shred or pull apart all of the meat, separating out any of the remaining fat.