Bad idea if you decide on having them join the party.
First off, you don't want the NPCs to steal the show. The game is about your players not the uber npc who somehow is able to overcome everything and spouts off lame one liners during a fight. If you play the character like he is characterized in the show, and he somehow overcomes everything, your players may start resenting him.
Secondly, if you put those characters in the game, don't be surprised if your players decide to assassinate them. If your players do kill off Naruto, DO NOT raise him from the dead. Also, no not act like you were surprised that the players would decide to attack him. More importantly, treat him like a normal npc: give your players EXP for killing him and give them his treasure/gear.