First anon gave some good advice. The only thing I can think to add is don't play him with the expectation of that reaction from others. Canon characters removed from their canon are always going to get different reactions from others than they receive in canon because they're being taken out of a world crafted with them in mind.
For example, Buffy out of the Buffy-verse might still be tough, but there are many other canons with characters who make hers seem like normal humans are to her. She isn't going to be the toughest kid on the block in a jamjar that allows powers. She shouldn't be played with the expectation that she is, and OOC expectations often come through IC behavior.
Study what makes him charming to the characters in his canon, bring those qualities to the RP, but don't get flustered if he's not as charming out of his canon world as he is in it.
Re: [General] Playing "charming" types.
For example, Buffy out of the Buffy-verse might still be tough, but there are many other canons with characters who make hers seem like normal humans are to her. She isn't going to be the toughest kid on the block in a jamjar that allows powers. She shouldn't be played with the expectation that she is, and OOC expectations often come through IC behavior.
Study what makes him charming to the characters in his canon, bring those qualities to the RP, but don't get flustered if he's not as charming out of his canon world as he is in it.