Children who watch violent cartoons will become more aggressive.

According to Albert Bandura's Bobo Doll Experiment, yes. When children were exposed to videos of an adult model abusing and hitting an inflatable Bobo Doll, the children reflected the behavior of this adult when presented with a similar doll, using their fists, hammers, and other objects to hit the doll repeatedly and aggressively. Similar experiments have shown links between exposure to excessive violence and children displaying these behaviors since, however the results have been up for debate for years.