In addition, it is also a crossover with fellow series, NCIS: Los Angeles which is a spin-off of the original "NCIS" series. The storyline that began in this episode later concluded on the NCIS: Los Angeles Season 3 episode, "Touch of Death". This episode also marks the debut appearances of NCIS Special Agents Sam Hanna and G. Callen, both of whom are main characters on NCIS: Los Angeles.