[ That sure is some interesting intonation combined with a total lack of contractions, Aigis. But Lelouch doesn't obviously stare at her, just files it away. ]
There are a variety of different rules by which Halloween costume selection could be said to function. [ Not that he doesn't sound pretty mechanical himself sometimes. Pushes aside a costume on his own rack with something of a flourish, and tugs something out to better look at it. ]
For example, it's considered traditional to dress up as something 'scary'.