Spawn modified prefab

I am trying to spawn my playerprefab as npc so it has the "npc" tag and disabled InputControl.
Something like this:
Void SpawnBall () {
GameObject npc = (GameObject)Instantiate (playerPrefab, position, rotation);
npc.tag = "npc";
npc.GetComponent<UserControl>().enabled = false;
NetworkServer.Spawn (npc);
}
Still the client spawns the original playerPrefap.
What am I doing wrong?

 

Well if you look at your instantiate line, you choose the playerPrefab for the object you're spawning.