Media Shapechanger
There are a number of things someone can do to rub me the wrong way in a gaming situation, but one of the fastest is to tell me, "Oh, X [my character] is just like so-and-so from..."
I figure a source is just that: a foundation. It's my job to take my skill in sculpting that source to add the little details that change it from the simple fundamentals of someone else's creation into something I can use. It's not a question of mimicry (or imitation being a sincere form of flattery), but my pride in design, my art.
Don't get me wrong: there are characters out there I wish I had created. Their shadows may populate the worlds I create, but they are not my characters, and despite my fondness for fan fiction, if I'm using a character, it's my own character. It might have things in common with "so and so," for there are lasting archetypes that attract gamer minds, but I am not running someone "just like" so and so.
I was embarrassed to play V (from "V for Vendetta") in Bolthy's Luke & Merle Adventure. Or Granny Weatherwax (from TP's Discworld novels) in the Courts of Chaos Con 2001 LARP. And I thought I did fairly well in both cases.
I know there are a number of people who design both characters and plots around existing media. I'm a lot more generous in regards to plots (unless it's too obvious an imitation) but I try not to weave my characters to a common pattern. It's why I'm hesitant to use characters from game to game, unless I know that each new scenario will bring out new aspects of those characters.
After all, life is a learning experience, even for my imaginary lives. [grin]