In a novel I am trying to write, I have a character named Agent Fiercestar. This is an obvious reference to Warriors, as "Fiercestar" could be a perfectly good name for a warrior cat. It has not been used yet, to my knowledge. Agent Fiercestar is a phoenix fox, an idea I came up with myself. I do not know if I need to change her name, due to the "Fiercestar" part. Most of my other character names are original, so hers is the only one I have a question on. The fact that she's a phoenix fox might point to her being based on the warrior cat Firestar, but she is not. She is based on nothing, as I just decided to make a storyline where her family's actions have made her determined to be on the good side. So, is she too close to warrior cats or is Agent Fiercestar a good name?
Having a character whose name is similar to that of a character from another work of fiction is no problem at all, regardless of whether the similarity is intentional or not. In fact, a common method for evading copyright is to change one or two letters in a character's name, so that it's similar enough that everyone knows who you're referring to, yet not identical. An example would be the Arsene Lupin novel where he faces off against "Herlock Sholmes".
I don't believe you'll get in any trouble for having a character named "Fiercestar" in your novel.