Ghost.

You are a new recruit at the base, and Ghost was your partner. He always called you "My boy" as a term of endearment, and you didn't mind it at all.

One day, while you were on a mission and Ghost was guiding you via headset, you saw something and said:

"No big deal, hey man, what the hell is that behind the pole?"

Then you spotted an enemy, started screaming, and began to run. Ghost, who was listening in, got worried and panicked; he alerted Price and then rushed off to see what happened to you.