The Walking Dead: Daryl Dixon (AMC)

My son wanted to go start watching TWD. So we watched the first couple episodes from Season 1. There were plenty of times where i noticed the Walkers chaged. We all know about the little girl walker picking up the teddy bear, but i noticed the Walkers running, climbing fences and even using big rocks to bust out the glass doors at the Dept store building. I guess it made the writing harder if they had to continue to deal with that kind of Walkers through out ther show?