When children see a behavior that they repeat you are talking about the concept of modeling. Modeling is a mirroring or parroting of behavior that a child has seen a role model or caregiver complete. When watching a TV show that they enjoy or that they view as "good" they will want to model that behavior as this is a desireable behavior. If a child watches "Veggie Tales" and sees these behaviors as desirable they will be more likely to immitate the behaviors seen here. Likewise if a child see's violent shows and views these as "good" they are more likely to mimic the violent behavior.
This concept was illustrated in the Bobo Doll Experiment where they took a group of boys and a group of girls in a nursery school to see how children learn aggression through observation. In this experiment they found that children who were exposed to violent behavior against the bobo doll were more likely to repeat the violent behavior themselves.