She was a martini glass, and her son was an olive. It worked perfectly and hilariously, and while it may not have been the best costume of the night it was certainly up there. Of course caribbean pirate costume for infants don’t have to be group costume events, though considering that your infant will likely not remember what you did or didn’t dress them as, I say it’s best to come up with a theme the whole group can enjoy. Plus, later in life, you can show them pictures of when you dressed them as an olive. Any parent should enjoy the chance to do that!