"If Yoda and Sidious were pupils together, wouldn't Yoda then know that Palpatine was a Sith Lord from Day One?"
Reply:
Yeah nice point.
Have to re-watch episodes 1, 2 and 3 to see if there is EVER a scene when Yoda and Palpatine ACTUALLY meet each other to talk about anything.
i.e. Perhaps they never encounter each other in these episodes.
So, if they never meet once, then the story would make sense. Although I guess, Palpatine could have just been that good at convincing everyone (including Yoda) that he wasn't evil:
You probably have all heard the saying: "The greatest trick the devil ever did was to convince the world that he didn't exist" which would proabably apply here.
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Note: Because I am also a die-hard Stargate fan my variation on this saying is as follows:
"The greatest trick the devil ever did was to convince the world that he is GOD."
Tell me what you think of this variation.
If you watch Stargate, you might get this - i.e. The Gaould convince people that they are Gods, when they are obviously not.
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But yeah, if anyone has the time to re-watch these episodes let me know of a scene when they meet, in which case I'd have to revise my plot. Probably don't have to check episode 3 because the only time when they meet is when they battle near the end.