The scenes in Alaska were shot in secrecy.
When Special Agent Parker enters Gibbs' basement, looking for Gibbs, he sees that one of the basement walls has been dug out. At last, we see how Gibbs got the boat he was building out of his basement.
This was David McCallum's first appearance of the season, and also the final episode to feature McCallum and Mark Harmon together before the former's death in late 2023.
Gibbs actually revealed how he'd get his boats out in ep "Honor Code", Nov 1, 2005. (Season 3, ep in).
To settle some confusion: When Gibbs and McGee are talking near the end about the number of cases, Gibbs asks "How many cases do you think I've worked?" to which McGee asks "Oh, you mean in 25 years (which is inconsistent with other episodes where it was established Gibbs joined NCIS in 1991, when it was NIS, making it 30 years)? At least a thousand". The question and answer was referring to the number of career cases Gibbs worked on while working as a Special Agent for NCIS and not about how many cases nor length of time he and MeGee worked on.