Imaginary Friend?

Took the boys for a well visit today. Kinda late but I finally got it done. I dread going there especially when the kids are well. We spend hours there, literally, and they always seem to catch something. Our appointment today was at 8:30am. We didn't see the dr. till probably 9:30 or 10 and finally got out around 10:30. Matthew got 4 shots, poor kid, and he "screamed like a girl"...he really hates/fears shots. Cameron got 1 and took it "like a man". But the most memorable part of the visit for me was when the nurse asked Matthew if he had any imaginary friends. I'm not sure he understood, so she asked him "when no one's around do you pretend to had friends" and Matthew said "No, I just call my brother to play". Ha. Is that a standard question? It seemed weird to me.