Growing up, we were too poor to afford real costumes. Most years it was one of those cheap plastic masks (You know the ones.)
But - one year, my mom decided to just put me in one of my sister's dresses, slap a (clean) mop head over my hair and send me out. No undies, sadly - but hey you can't always have everything.
I secretly loved it, but didn't say much. I was too Scared to speak up for myself back then about ANYthing, let alone my wanting to be a girl (long story and not for this forum)
One of the neighbor ladies loved my outfit and I can still remember the phrase she used. She said I was "The cat's pajamas." I'd never heard the phrase before, so it stuck in my memory.