Finn as he will appear in the series.

Finn is a 13  Saiyan and is the main hero of Adventure Time Z. He met the rest of the heroes when he went through a portal after the Ice King. Finn came after the Ice King and ended up in their world. The Ice King had kidnapped Princess Bubblegum then Finn and Jake invaded the Ice Kingdom. Killing all of his ice monsters and just simply throwing his penguins away, they saved Princess Bubblegum. Then the Ice King reveled his vortex traveling technology, then when in after them greeting Princess Bubblegum a good bye. As Finn prepared to leave the Princess as why he was leaving Finn quoted "I cannot let the Ice King destroy another world, I must kill him". The heroes are attacked by the Ice King's Ice Minions and are nearly killed until Finn and Jake come and save him, they then explain to them there situation and they all train, Finn and Jake learn the Kaioken and after another Ice Minion ambush Finn has a near life death experience and is given a senzu. With the power up Corey and Drew are sure he is in fact a Saiyan. Finn tries to deny it saying he's a human but they say with all that power he must be a Saiyan.