It is I/It is me
Both "It is I" and "It is me" have been common in English usage for centuries, the former tending to be used in more formal contexts, and there has been considerable debate among grammarians about which is "correct":
From the beginning in the 18th century, there were two camps. The earlier, apparently, is represented by Priestley 1761 [The Rudiments of English Grammar], who favors accepting it is me on grounds of custom... Lowth 1762 [A Short Introduction to English Grammar] heads the partisans of it is I, who clearly had Priestley outnumbered: Baker 1770, Campbell 1776, and Lindley Murray 1795 were on the side of the nominative. And these were the commentators whose preachments were accepted as gospel by the schoolmasters.
This preference could be due to the model of Latin, where the complement of the copula is in the nominative case. The practice of trying to model grammars of English on that of Latin has, however, fallen out of favor, and linguists today describe each language on its own terms.
Fiction writers have occasionally pointed out the "mistakes" of their characters in an authorial comment. In "The Curse of the Golden Cross," for example, G. K. Chesterton writes, "'He may be me,' said Father Brown, with cheerful contempt for grammar." And in The Lion, the Witch and the Wardrobe, C. S. Lewis writes, "'Come out, Mrs. Beaver. Come out, Sons and Daughters of Adam. It's all right! It isn't Her!' This was bad grammar of course, but that is how beavers talk when they are excited."Wikipedia