Joanna Merlin has portrayed two different characters during the course of the series:
- Episode 2.21 Silence (1992) - Carla Bowman.
- Episode 3.19 Virus (1993) - Carla Bowman.
- Episode 5.8 Virtue (1994) - Deirdre Powell.
- Episode 6.18 Atonement (1996) - Deirdre Powell.
- Episode 8.12 Expert (1998) - Deirdre Powell.
Guest stars Vera Farmiga and Richard Hughes both appear in Martin Scorsese's film The Departed (2006).