Write a narrative about an ordinary day at work or school which takes a turn for the extraordinary when you realize there's an unseen visitor interacting with your environment. The visitor can be friendly, mischievous or even slightly sinister. What signs lead you to their existence? What actions do you take to communicate with them or unveil them? How do your colleagues or friends react to these strange happenings? Flesh out this scenario with an emphasis on vivid descriptions and character reactions.