You knew Letterman’s writers would be all over this:

10. You describe her to friends as “a nondescript female with eyes and hair”

9. ”Photo” of girlfriend looks suspiciously like SunMaid raisin lady

8. You keep referring to her in the first person

7. Have a patent pending for a machine that gives you a hickey

6. Someone says, “Tell me about your girlfriend,” you say, “Hmm…let me think of something”

5. Your imaginary friend is dating her sister

4. Everyone can tell you’re arguing on the phone with Siri

3. She’s never upset when you forget her imaginary birthday

2. Always pressuring you to pretend to buy engagement ring

1. Said she’s too shy to meet your friends, your family, and you

David Letterman - Top Ten Signs You Have an Imaginary Girlfriend