Mix together the barbeque sauce, italian dressing, brown sugar, and Worcestershire sauce.
Place frozen chicken in the crock pot and pour sauce mixture over the chicken. Cover.
Cook on low 6-8 hours (3-4 hours on high if you're in a hurry)
Remove chicken breasts and shred. Add back into crock pot and stir together with sauce remaining in the crock pot. Serve on a bun.
*I brush the buns with garlic olive oil and toast them before serving.