The use of the term “spirit animal” to mean something you really like or identify with, especially in a joking manor, is a form of cultural appropriation. If you google that, you can find some good resources. Here are a couple:
Here’s a succinct explanation from Tumbler user garconniere that goes all the way back to 2011:
yes, i am really uncomfortable with how often people say “person x is my spirit animal” or just randomly tag things “spirit animal” without thinking about it. for the longest time i didn’t get what it even was supposed to mean… just look at the tag on tumblr and you see hockey players, fictional characters, movie stars, “hipster animals” and hey! even a few animals. it has come to my attention that it is trendy to throw a “spirit animal” theme party. (for the record, this is just dressing up as animals)
just take a second, step back and think about it before you throw around a term like spirit animal. is there a better way of saying what you’re actually trying to convey? if you’re talking about a person, could you say, “i have a lot of admiration for you/we’re kindred spirits/you’re my brother from another mother/sister from another mister?” if you’re throwing a theme party, could you just throw an… animal themed party?
