Is this copyright?

You can't use copyrighted or trademarked properties without owner permission. Minecraft is a trademarked property. You need to obtain a license from the owner to produce items for sale. What others may be doing illegally doesn't make it OK for you to do it.

Yes, you can get in trouble if you use the Minecraft name and/or represent it to be connected with it or the company who manufactures it. Many people think corporations don't care, but my friend used to make little plastic earring that resembled Mickey Mouse and DISNEY contacted her with an threat to cease and desist. Companies HIRE people to scour the Internet searching for copyright infringement. What you could "possibly" do would be to call it a "Minecraft-inspired" plush .. that might provide a bit more leeway. But, if contacted (officially), do what they tell you and STOP.

It is copyright infringement. But it's up to the copyright holder to identify violators and enforce it. Usually small time sellers can fly under the radar, it's more effort than its worth to hassle you. If you try to mass produce your plushies and start making a substantial profit, then you might have a problem.

no it's not legal without getting written permission and paying a licensing fee and royalties - you could get sued big time