You mean apart from the fact that Samus is based off of her Zero mission look, the stage we got isn't in any Metroid Prime, Samus's bombs are the 2-D styled ones and her missiles are Super Metroid based as well? and if you want sources go and look for your self.
This point has actually been argued many, many, many times before in the Ridley thread and it has always been found out that nothing is from Prime.
And you make out as if Ridley is retro when... he isn't. He is nostalgic and he makes appearances in recent Metroid games as well. Not to mention he is the most powerful space pirate that you ever get to see and he is a reoccurring boss and he caused ALL the events in the Metroid series to happen )Find the origin of Samus's hatred for the space pirates) and even if you don't include the fact that Ridley killed Samus's mother in front of her eyes and caused her dad to commit suicide, he still stole the Metroid's and he was still on space frigate orphan (Or whatever its called), and he still over sees most of the space pirate activity.
He may not be the final boss but he is the main antagonist and Samus's arch rival.
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