So many good memories, considering that I worked for a major thrift store chain where Hallowe'en was our biggest season. The memory I have is where we always did a Costume Catwalk to showcase the products we sell. My wife was a front end manager, so she specifically chose a knight costume for me and put some extra oomph in her description when I walked up. Sounded like a regular thing to customers, but our co-workers giggled because they knew exactly what she meant.
Another time was when I went full costume as Drizz't Do'Urden to a bar, and won first place for best male costume.
EDIT: I should mention that I won despite nobody in the bar knowing who the hell I was cosplaying.