The child needs to understand that it is bring a bear, not, bring a soft toy, dragon, fairy, unicorn, sea lion or limpet ffs. It is YOUR job op to teach him this
hear hear!
too many parents, it seems, are not prepared to tell their DC "no". Too many are willing to create merry hell over every little thing that they disagree with rather than tell their little precious no, you dont get your way this time - and have no qualms about letting the child know they will have a go at the teacher for them. These type will be the ones all daily-mail-sad-faced on the front of the local paper when their DC are older and have been excluded because the parents "don't see why they are so strict on uniform/hair style rules" etc.
What happened to supporting the school?
There is a big difference between an end of term treat "cuddly toys picnic", for fun, which I have every year with my RAinbows and we have dolphins, unicorns, tigers and goodness knows what - and one expressly planned to fit in with a topic on the 3 bears.
DD did a half term on bears in reception - you might wonder how they spin it out to cover so long and every area of the curiculum, but it was brilliantly done. They made porridge (weighing and measuring), masks, made up scripts with bear puppets on sticks, went for a walk in the woods and looked at types of trees birds and flowers, had lots of stories about different bears from winnie the pooh to paddington and of course Goldilocks & the 3 bears, including learning "we're going on a bear hunt" in French. They compared sizes of bears, types of materials for building houses/beds/chairs, talked about strength, softness and other physical properties and ranked other objects in terms of big/small/medium sized, like the 3 bears.
If the teacher says yes to a dragon toy, she has to say yes to a noisy robot next.
If OP makes a fuss about this, instead of dealing with it sensibly she will be branded One Of Those Parents, and deservedly so.