The motherfucking 4th hokage came out of fucking nowhere and nobody cares because apparently they got Wile E. Coyote and the Road Runner to animate this week's episode.
I simply took it as a programmed personality/hologram/whateveryouwannacallit that's part of his seal.
The seal was designed so that Minato pops up and helps Naruto somehow - with the end result being Naruto has 100% control over the Kyuubi without consequence.