Nothing makes your friends and loved ones wonder what they ever saw in you quite like wearing a racist costume to a Halloween party, and if you manage to get out alive you'll never outlive the stigma of your racial insensitivity.
But unless you showed up in blackface, wearing a Klan hood or dressed as the Führer himself it's probably not your fault, because it can be hard to tell which costumes are acceptable and which are downright racist.
That's why Dan Hopper from CollegeHumor put together this handy dandy flowchart to help us navigate the seas of racial tension and reach the shores of racial harmony on Halloween.
-Via CollegeHumor
Historically, geisha would entertain patrons in completely non-sexual and non-titillating ways. They would even perform in brothels for men waiting for the actual prostitutes. This is why we ridicule "sexy geisha" costumes.
Don't get me wrong, I'm not saying this is somehow "NOT ALLOWED" or anything. Just that there are valid reasons people don't like costumes like these, and if you want to be polite you should heed those reasons.
Or "Lies My Teacher Told Me: Everything Your American History Textbook Got Wrong" .. https://en.wikipedia.org/wiki/Lies_My_Teacher_Told_Me .. ?
Or "Indian Givers: How the Indians of the Americas Transformed the World" .. https://en.wikipedia.org/wiki/Indian_Givers:_How_the_Indians_of_the_Americas_Transformed_the_World .. ?
No one is expecting you to do a dissertation. But if you claim to admire someone without having learned a little bit about who they are, you will get called out for being superficial. Personally, I think expressing passion for a person (or any topic) while being shallow about it, is far worse than being inconsiderate in the course of light-hearted fun.
And the only specific people I've imitated by costume are ones I've known personally and for whom I was reasonably sure they could take a joke. There are so many possible costumes out there, even with budgetary or other constraints, it is easy to have fun while simply avoiding obvious baggage.