Hank wants to be a dragon for Halloween. He says to his mom, "I want to be a dragon for Halloween". His mom says to him, “You shouldn’t be a dragon for Halloween, you should be Minnie Mouse.” (So Hank is Minnie Mouse for Halloween and is sad.)
Tyanna wants to be Indiana Jones for Halloween. She says to her dad, "I want to be Indiana Jones for Halloween". Her dad says to her, “You shouldn’t be Indiana Jones, you should be Barney.” (So, Tyanna is Barney for Halloween and is angry.)
Eric wants to be a clown for Halloween. He says to his parents, "I want to be a clown for Halloween". His parents say to him, “You shouldn’t be a clown for Halloween, you should be a cucumber with a hat. (Eric yells while he falls down because he’s scared of cucumbers with hats.)
I often have the kids write their choice of Halloween costume on a piece of paper and I collect them. I then draw them out of a hat and ask “Who wants to be [insert costume] for Halloween?” and circle those before settling on one student.
Another good option is to explore one student's Halloween history by talking about what she wanted to be "last year" or "two years ago" or "when she was 10 years old".