Have you ever kissed a girl only once?

I met a girl a few months ago who started grilling me from the moment we met.  She rapid-fired question after question:

• How old are you?
• Where were you born?
• What is your place of employment?
• How long have you lived at your current address?
• What does it mean to have free will?
• How many tennis balls roughly would it take the fill all the worlds oceans?
• Can you envision a scenario where you would have to choose between saving my life and that of a South American football team?  And which would you choose?
• How many people have you met?
• What is your weight in stone?
• Do you always eat breakfast?  Lunch?  Brunch?
• Have you ever jumped out of a plane?
• Have you ever kissed a girl only once?
• Do you know your social insurance number?
• Do you know what the Fibonacci sequence is?
• Do you remember Teddy Ruxpin?  What about his caterpillar friend?
• What should I do about this cockroach situation?
• What is your second favourite colour?
• What is the x to your o?
• This isn't going well, is it?

And so on and so on.  It was truly a brutal assault.  She was hot, mind you, but this was crazy.

After dinner, I kissed her goodnight and silently vowed to never see her again.  Though the question didn't make sense to me at the time, I realized then the meaning of kissing a girl only once.

And I still don't know what the x to my o is.