Smocked shirt theme ID… Halloween themed, or specific?

Location is southern United States.

I go thrifting a lot to find clothes for my son, and I have a soft spot for smocked clothes. Found this shirt, and I assumed that the characters were just general Halloween references, so I bought it. Now looking at the shirt again, I’m not so sure. Google image search came up with nothing. I feel like it may be a reference to a specific show/movie or something. Anyone have any ideas?