Actress Olivia d'Abo plays Goren's arch nemesis in multiple episodes; to catch the whole fight between the two, she plays Nicole Wallace / Elizabeth Hitchens in the following episodes:
- Frame (2008) ... Nicole Wallace
- Grow (2005) ... Nicole Wallace
- Great Barrier (2004) ... Elizabeth Hitchens / Nicole Wallace
- A Person of Interest (2003) ... Elizabeth Hitchens / Nicole Wallace
- Anti-Thesis (2002) ... Elizabeth Hitchens / Nicole Wallace
Daniel Oreskes has played three different characters over the course of the series:
- Episode 4.15 Death Roe (2005) - Duke Caldwell
- Episode 6.9 Blasters (2006) - Zim Flamur
- Episode 7.22 Frame (2008) - Det. Fontanella