1.) Boba Fett. I remember reading interviews with Lucas, pre-PT, in which he confessed to being mystified by the overwhelming popularity of Boba Fett. If I recall correctly, Lucas even referred to him as a "nothing character." Maybe that's why he polished him off so abruptly in ROTJ.
So what did he do with this "nothing character"? He created a whole backstory for him. And a lame one at that, which seems like nothing more than an afterthought. And then what did Lucas do? Promptly abandoned the character yet again.
It's pretty obvious that the only reason Boba Fett figured into the PT at all was because there was a massive fan base for the character, and Lucas wanted to take advantage of it somehow.
2.) Jar Jar Binks. Here we see the polar opposite of the Boba Fett phenomenon--George Lucas diminished the role of the character in response to fan disapproval.
While I'm willing to grant that Jar Jar's role would have been diminished anyway (it's hard to see how he could have figured into the rest of the trilogy), I have no doubt that Lucas would have employed the character as alleged "comic relief" to a far greater degree, had there not been such a huge outcry of hatred for the Gungan among the general public.
I'm sure there are plenty of other examples that others can come up with....
This post has been edited by Devout Catalyst: 23 May 2005 - 10:22 PM