PalpatineWarning: Wikipedia contains spoilers.
The Sith lord Darth Sidious bears a suspicious resemblance to Palpatine, and seems to have the same evil ambitions, but whether they are in fact one and the same person will not be revealed until Star Wars: Episode III.
In Star Wars Episode II: Attack of the Clones, which is set ten years later, Supreme Chancellor Palpatine further manipulated events to make the Senate grant him dictatorial emergency powers by engineering a Galactic conflict. He later proclaims himself Emperor and establishes the Galactic Empire (these events have not been seen in any Star Wars film, but it is conjectured that they will be depicted in Star Wars Episode III - currently in production). He then dissolved the now-Imperial Senate in the fourth film Star Wars Episode IV: A New Hope.
In the second Star Wars trilogy, Palpatine is known simply as "The Emperor". Through his servant Darth Vader, he tries to make Luke Skywalker join the Sith (those who follow the dark side of the force), but in the end (in Star Wars Episode VI: Return of the Jedi) his plot fails, and he is killed by Vader, who turns from the Dark Side at the last moment.
Like many personalities in the Star Wars universe, Palpatine's character was clearly inspired by certain historical figures. Parallels to Julius Caesar, Napoleon Bonaparte and Adolf Hitler can all be found in the Galactic Emperor's words and actions. In writing the original drafts of the Star Wars films,in the mid-seventies, George Lucas has said he was influenced by then-US President Richard Nixon.
Palpatine was given the first name "Cos" in a draft script for Return of the Jedi and many Star Wars Fan fiction writers have since used it in their stories and web pages - so much so that it has become fanon.