I saw an image of Charlie ( https://e621.net/posts/3120080?q=smiling_friends ) that is looking pretty dire in the approval department. 3 of 3 reviewers believe it is not relevant.
I would like to argue that the main characters of Smiling Friends do in fact qualify as relevant, as they are non-human.
TWYS: if you watch the show, you'll see plenty of visibly human characters juxtaposed with the main characters, whose character designs are visibly very different. It's safe to say based on that alone that the main characters are non-human by TWYS rules.
Canon/word-of-god: Zach himself said that the main characters are non-human "critters" that live alongside in-universe humans.
To my understanding, furry isn't the requirement for being relevant to e621. The requirement is that at least one character in any image is non-human, with a few caveats like it can't be a solo human being tentacle fucked because the tentacles don't count as a character, etc. This rule does allow images that depict pokemon trainers fucking their pokemon, or to my understanding, solo images depicting humanoid characters such as trolls and elves. I'm not sure what the stance is on very human-looking characters like Hylians from the zelda universe.
Correct me if I'm wrong or missing something here.