I too always thought that it was just too obvious that Palpatine and Sidious were the same purpose. I knew that Senator Palpatine would become Emperor Palpatine from day (er, episode) one. I just did my best to resist the idea that he was Sidious. I always thought that maybe the two would cross paths at some point, and Sidious would help Palpatine take over or something. Or maybe I'm just making that up now. I can't remember. It's been too long.