DS is going as George from George's Marvellous Medicine.
It's quite timely, as we recently read it.
He's not one for keeping costumes on. Masks annoy him and he can't wear them with his glasses, he's not keen on face paint, he gets too hot in costumes, or too cold, or they get in the way when he wants to play.
So we try to aim for reasonably normal clothes and use props.
We are about to make some Marvellous Medicine in an empty plastic bottle (half baby oil, half water coloured with food colouring. Apparently once you swish it about it looks like a galaxy of stars in a bottle, I got it off Pinterest so hopefully it works).
I've printed a label saying Marvellous Medicine, and printed a picture from the book, of George mixing the medicine, and typed George underneath it so DS can wear it like a badge and people will know who he is.
And I've made this. It's the shrunken Grandma from the story, for DS to carry.
But, you could easily make something similar by printing off a picture of grandma and sticking it on cardboard. It doesn't have to be sewn. And if you print a reverse image you could stick it so both sides look like grandma.