The diner where Bishop and Gibbs first go meet the original investigating detective is the same diner where Jenny Shepherd was killed. You can tell because the outside of the building including the entry doors is identical with the paint scheme being to only difference.
This is Mark Harmon's 400th episode playing Leroy Jethro Gibbs. The character debuted in Ice Queen (2003) and Meltdown (2003), a two-part episode of JAG (1995). This is the 394th episode of NCIS (2003) (note that Judgment Day (Part I) (2008) and Judgment Day (Part II) (2008) aired as one two hour episode on the same night). Harmon played Gibbs in four NCIS: New Orleans (2014) episodes: Breaking Brig (2014), Sister City: Part II (2016), Pandora's Box, Part II (2017), and See You Soon (2018).