Christina Cox, of Nikki & Nora cult fame, turns up as a girlfriend in the same episode.
John Billingsley (Dr. Phlox) and Connor Trineer (Charles "Trip" Tucker) guest-starred together in the 11/18 episode "Red Moon."
And Hoshi consulted with the CBI (ep 3x12).
The show is loaded with former 24 cast members. Just a couple examples are Gregory Itzen (Charles Logan) as Virgil Minelli and Leslie Hope (Teri Bauer) as Kristina Frye. Carlo Rota (Morris, Chloe's husband) also appears as a Russian red herring suspect named Dimitri Zubov.
Morena Baccarin (a.k.a. Anna, Inara, Adria) is a matchmaker, recently widowed, in the episode "Every Rose Has Its Thorn."
Screwed by the Network: Fans have been accusing CBS of this since Season 5. First they put the series in a graveyard shift (10 PM Sunday), then every so often they forces it to compete with football and other highly-rated shows. At the same time, the series itself has seen its share of critics increasing since Season 4, who accuse the writers of pulling The Chris Carter Effect with its Red John Myth Arc.