John Cunningham has played five different characters over the course of the series:
- Episode 2.11 His Hour Upon the Stage (1991) - Cobb.
- Episode 3.18 Animal Instinct (1993) - Donald Walsh.
- Episode 5.2 Coma (1994) - Max Weston.
- Episode 7.14 Working Mom (1997) - Daniel Metzler.
- Episode 9.7 Venom (1998) - Daniel Metzler.
- Episode 9.22 Admissions (1999) - Mr. Crowley.
- Episode 12.12 Undercovered (2002) - Daniel Metzler.
- Episode 18.4 Bottomless (2008) - Daniel Metzler.
Chris Noth (Detective Mike Logan) & John Cunningham (Donald Walsh) also worked together on Feeding the Rat (2011) (episode 3.4), as Peter Florrick & Gene Osterman respectively.