Place chicken in a slow cooker. In a separate bowl, mix the barbecue sauce, Italian dressing, brown sugar and Worcestershire sauce until well blended. Pour over the chicken.
Cover. Cook on high 3-4 hours or low 6-8 hours. It looks like it's almost TOO much sauce, but trust me, after you shred the chicken, it's perfect.
About 30 minutes prior to serving, shred chicken. You can do this inside the crockpot, or by pulling the separate pieces of chicken out and onto a plate, shredding them, then returning it to the sauce. Honestly though, this part is simple no matter how you do it- the chicken is so tender it shreds easily.
Return shredded chicken to the crockpot and stir into the sauce. Cook remaining 30 minutes. Serve on a hamburger bun and ENJOY!