I've been watching the Dragonball series for weeks now and I was thinking,that the Sonic the Hedgehog Series are very similar.For example, they both got to collect seven items(Dragonballs and Chaos Emeralds),they have a super transformation(Super Sayian and Super Sonic etc.),there was one episode in Sonic X where Sonic was wearing a scouter,just like Dr.Gero,Dr. Eggman(or Robotnik) creates robots and other mechanical things just to take over the world(even though Dr.Gero creates Androids not Robots),and there was even an episode in Dragonball where Goku was using his tail to fly just like Tails!Well that's all I know so far, if you got more similarites comment.