Why are so many convinced Lucina is full on newcomer and a full on character? She is not a clone of Marth, she is a literal copy and paste with a different skin so I have a theory about her. You see in the game Naruto Clash of Ninja 2, there was the unlockable character Mizuki. However what made him special was that he didn't actually appear on the character select. Rather, he was an alternate costume for Iruka that the game treated as a seperate character. His moves were 1:1 identical to Iruka but with some slightly different animations suchs as his taunts and victory pose. He also had completely seperate voice clips and the game deplayed Mizuki's name instead of Iruka. I believe this is what Lucina is, an alt for Marth with a different voice, different taunts, different entrance and victory animations but with a perfectly matching moveset. This is also likely how Female Robin works, an alt for Robin with different sounds and animations.