File this one under, “Just because you can, does not mean you should.”
A colleague had called my attention to the fact that, in Windows 10, you are allowed to use emojis in file names. (Press the Window key + . to call up a dialog that allows you to select one.) I was pretty sure AutoCAD would have a problem with that, but I was surprised to find that I was able to create a file called 🍕.dwg and AutoCAD had no problems with it.
I do not recommend doing this with project files. I will also note that I did nothing beyond creating the file. I have not fully tested this. For example, I did not see what happens if I try to externally reference this file, or even just inserting it as a block into another file.