Ok, this made me mad enough that I went online to type out this whole thing. From the top left, Nagisa, a man, who is disguised as a girl in this one very specific case. The reason it works is because his mother wanted a daughter and so tries to make Nagia act and dress like a girl. It's obvious he's a guy, even more so when he's out of disguise. Next, I don't remember the anime, but it's clearly a girl. Next, Crona, has no stated gender but is one or the other as hinted by Ragnarok. Next is Lu
ka who is biologically a male in most world lines, but is female in a few. He's not both at the same time. For all the similarities, they are different entities. Squid Girl is really sad because A. it's a cute girl show with anthropomorphic animals, something that is both very common in and out of anime and B. it's not even her true form. Taiga, is short. That is part of her character. But it's anime so it's clear she's at least a teenager. Putting all biases aside, she looks 15 to 16, which considering that being the point of her character, isn't too far off. idk who the next guy is, but he looks older. Different anime have different art styles, this is not shocking. It's only meaningful in comparison to Taiga, which is massive cherry picking. ... ... . I'll give you Felix. Spoilers from here on...
Koro sensei was a human, but was genetically modified into the squid we love. This comparison is stupid. Even if you want to argue he's technically still human, that's like going up to an old lady and calling her a baby, cause she was a baby at one point. Again, Red Blood Cell is anthropromorphized. It's a way of giving non humans human characterization. I get that it's a bit extreme, but it's all for the point of the metaphor (and for marketing so I'll give it a pass). Shiina is not literally a pet, it's a title given to her due to her current circumstances with the protagonist. That's like if I said someone was cool as ice and then you thought he was literally below freezing. I'll give you a pass on this one as well because I don't remember the show (I think it's the SNAFU show) but I remember looking talking about him. He still looks like a boy to me, but I've seen a lot of anime. That's the end.