Gibbs Rule #11: When the job is done, walk away.
At one point Abby comments to McGee that there were alligators in her backyard while she was a kid; both Abby Sciuto, the character, and Pauley Perrette, the actress, lived during childhood in the swamp or bayou country of Louisiana.
Gibbs Rule #12: Never date a co-worker.
"Semper fidelis" is Latin for "always faithful", and is the motto of the United States Marine Corps.
When DiNozzo and Rifkin meet, DiNozzo says "You can call me Al, I'll spare you the singing." This is a reference to Paul Simon's song "You Can Call Me Al".