The rhetorical device of spirit animals is nothing new, writes Megan Garber, and a concept that comes most directly from Native American spirituality. But the Internet has reduced it to ironic absurdity.
Garber dates this mocking appropriation of the idea to a Shroomery.org posting from August 2006, and tracks its proliferation on Tumblr. It earned an Urban Dictionary entry (free of reference to anything not Internet-related) by December 2010. The Toast summed up the inanity of its use in a glossary like so: "spirit animal: here’s something I like; I am not familiar with what a spirit animal is or does."
The clips above and below show two scenes from Fight Club (1999) which no-one seems to remember these days.