It's a plush toy that can be turned inside out, which Greta Thunberg famously had in the background of a picture of herself and her friends in support of Palestine. According to liberals on Twitter, it vaguely resembled an octopus from some antisemitic caricature; which (1) was only true in the way that the Big Dipper resembles an actual dipper and (2) if you make this kind of association unprompted it says more about you than about Ms Thunberg or Palestine

Iirc there was drama because Greta thunberg took a picture supporting Palestine with one of those autistic octopus plushies. Zionists thought the plush was referencing those propaganda posters with the big octopus covering the world with its tentacles.