Embracing constraints
I asked her what she wanted to dress up as and she said Cinderella (you can also go as a book character). I told her she could go as the dirty maid version of Cinderella but not the princess one. No princesses and definitely no Disney. She didn't agree to that. We talked more, trying to come up with something vaguely on theme. Her non-negotiable requirements were that it be something pink and something starting with C. Hmmmm.
By now I was starting to appreciate the challenge. Eventually we hit on something we both agreed on...a pink crayon. Her superpower could be her creativity. She liked the costume but not the reason. Thankfully there's a book called the day the crayons quit so I could justify it that way. Win.
Often when we're faced with constraints, we don't like it. We feel restricted and resentful. But if you embrace the constraints you may end up with a much more creative solution than if you just keep shifting the boundaries and end up with something standard.
Yes, you may create more work for yourself (my Sunday afternoon was spent trying to figure out how to actually make the costume we'd agreed on), but it can be fun. Creating something new is always more fun, no matter how hard.