It scared half the grad students because most of them aren't American and aren't really familiar with Halloween.
One of my most fun work Halloweens was the year I worked with a big company that had just brought on about 75 people from India, mostly recent college grads. They were there training on a long-term basis and were going to go back after a year and work with offshore teams.

The company had a tradition of different teams doing whole themed costume and decoration dealeos. The folks from India, who were integrated into the different teams, really got into it! It was fun explaining the whole concept, then convincing the onshore/offshore people that they should definitely participate, then planning things with them, then actually going to work and being dressed up and doing skits. It was especially cool knowing that for most of the guys and gals from India, it was the first time they had done that.