Ducky: I've learn't as much as I can from the dead. Time to start listening to the living. (00:34:20)
Ducky: See this fracture here?
Gibbs: Well...Yeah. You're pointing right at it. (00:16:50)
Abby: Aww, You shaved your mustache. I liked you with a little hair on your face.
Gibbs: I've still got my eyebrows. (00:08:45)
Singled Out - S4-E3
Abby: Awh, You and the director make cute Gibbletts Gibbs. (00:24:50)
Singled Out - S4-E3
Ferris: Look, I'm not a kidnapper!
Gibbs: No. You're just the dirt bag who ran away and left a woman to die. (00:17:50)
Singled Out - S4-E3
Tony DiNozzo: And if you find anything, make sure you call Gibbs. Not me. (00:14:20)
Agent Gibbs: Give me some good news, Abby.
Abbey: I'm not pregnant.
Agent Gibbs: There's a little girl who just wants to go home with her daddy. So will you help me... Please.
Agent Dinozzo: Did he just say...
Agent McGee: Yep.
Answer: I dont believe it is ever mentioned, but like most pilot episodes the characters are often changed, replaced or even removed in this case.