When you play a character that exists or existed, there's a stronger responsibility that you have. You owe that person and then you owe the family, you owe history, you owe the victims, the victims' families.
It really depends on what the screenplay is asking of you, and what your responsibility is to that character. You have the author's intent to deal with, you have the filmmaker's vision, and then you have your own wants, desires and needs for the character. It's collaborative. But I knew, right off the bat, that there was no way to go into some sort of pink-haired, clown-nosed character with Ronald McDonald shoes.
The only responsibility I feel is to deliver something that's new or at least to attempt that. The real responsibility is to entertain and to try and make people laugh.
