I'm often surprised when I learn about a unique hobby or special talent a colleague has, or when I observe him/her doing something outside of the professional box I've placed him/her in. When you get to know someone in the context of a work environment, you can come to view that person through the lens of the one role or the one setting in which you know him/her. It becomes easy to see people as...whatever you see them do every day. Into the profession box they go. If you never get to know them beyond their job descriptions, they can get stuck in it.
We box each other and ourselves. How often do we list what we do for a living among the first things to describe ourselves or someone else? Ask a person the question "Who are you?" and you're sure to get an answer to the question "What do you do?"
You and I naturally and unconsciously put people in boxes all the time. It's not always a bad thing. In fact, I think it can be a fantastic learning opportunity when a new piece of information comes along that causes us to re-examine the box we've created. (Side note: I'm not talking about the more harmful versions like cultural, ethnic, or gender stereotyping -- those can clearly be bad boxes to put people in.)
I actually find it humorous when people learn new things about me that don't fit with the professional box they have constructed around me. In a previous job, my boss was surprised when she saw me driving in my car for the first time. I had been working there for a couple of years, but she had never seen me drive. We both laughed at the situation -- and it's a trivial illustration of my point -- but I totally understand why it caught her off guard. At my current institution, a colleague in the marketing department was surprised when she saw a brochure I designed for my office. It was odd for her to see an "administrator" with an artistically creative side.
Several years ago, I was surprised to learn that one of the custodial staff at a school where I worked was in a jazz band. Several days ago, I participated in a diversity workshop, and was very surprised by many of the things I learned about my colleagues -- things I might never have otherwise known from our typical work interactions. I have a greater appreciation for them from the experience.
People are more than the work they do or the job titles they have. We have many identities -- the one that puts bread on the table or Benjamins in our pockets is only one piece of a larger, more complex puzzle that makes us who we are.