I don't have any problems remembering, er, ooh look, a squirrel!
Nicknames yes. It's only later that you realise you never knew the actual real names of most of them! I answered the crew room phone at Brawdy one afternoon.
Person: "Hello, can I speak to Flt Lt XXXXX, please."
Me: "Bottle? I'll see, hang on."
Person: "His name is not Bottle."
Me: "Oh, yeah, I mean Sid."
Person: "I'm his mother and is name is YYYY!"
Me: "Really? I never knew that. Hahahaha, wait till I tell the guys. I'll find him for you."
Phone: "Brrrrrrrrrrrrrrr"
Tu Chan Go, how long did it take you work out that you'd flown with 840 people?