Sean Cullen has played three different characters over the course of the series:
- Episode 9.12 Haven (1999) - Professor Davis Mills.
- Episode 14.7 Floater (2003) - Gene Marchetti.
- Episode 18.13 Angelgrove (2008) - Matthew Lortell.
Drew McVety has played three different characters over the course of the series:
- Episode 13.18 Maritime (2003) - Mr. Haas.
- Episode 15.19 Sects (2005) - Clerk.
- Episode 18.13 Angelgrove (2008) - FBI Agent.