My cousin’s family does themes. One year, they were all characters from the Wizard of Oz. The oldest girl was Dorothy, then came the Tin Man (homemade costume— it was actually really good), then Glinda, then the baby was the Cowardly Lion. Then another year (after the last Summer Olympics) my 8-year-old cousin was Michael Phelps! He thought it was funny to be a swimmer. It was a really easy costume— he went around in his bathrobe and a bathing cap and goggles.
My neighbor was also once a snowman one year when there was still snow. I actually couldn’t tell she wasn’t a real snowman. I got kinda freaked out when I saw it move.