Actually, I had a co-worker who had a phobia of zombies. She is an intelligent person. The logical side of her brain knows that this was a ridiculous fear. But phobias being what they are...
Anyway, she is constantly thinking about it, in the back of her mind. Any time she enters a new location that she'll be spending significant amounts of time at, she would scope it out to figure out the best escape route, in the event of a zombie attack.
Workplace. Friend's house. Classroom. Grocery Store. Favorite restaurant. Etc. She had a detailed escape-route planned for every location. And I do mean detailed.
Funny thing is, she's a totally normal well-adjusted functioning member of society. Bright, social, charming personality, all that good stuff. And you would never know she had this phobia if it didn't come up in conversation (like, debating the relative awesomeness or lameness of that stupid video game zombie movie series).
True story.