I wouldn't think a berserker mode would be such a difficult thing to understand. No poopdeville that isn't the Kyuubi, as DBZ and Sidnne said the Kyuubi is a very intelligent creature with a very distinct personality. What we have here is simply a berserker mode, as Jiraiya mentioned oh so long ago he used the key to loosen Naruto's seal and this is the result. He released more chakra than Naruto can handle so anytime Naruto goes beyond three tails, which is apparently the max he can handle, he just gets overwhelmed and goes crazy. Not until all nine tails are released and Naruto undergoes a second transformation into a giant nine tailed fox will the Kyuubi actually be in control.