For assistants on the phone interview I weed most people out. Just ask simple questions like: 1- What is your greatest weakness? 2- What do you like to do?
You'd be surprised at the answers I've gotten over the years:
1- I have none
1- I'm good at learning fast!
1- I'm very smart
2- I work hard
2- I'm really smart
2- {insert list of chores person does over a day}
If they can answer coherently the questions I ask over the phone, and I'm going to meet them, I always ask them to bring a dictionary.
Good tip on the banana part, I like it and I'll be using it in my current search for writers.