There are a number of actors from Slow Horses who all worked together on Wolf Hall: Aimee-Ffion Edwards; Jack Lowden, Jonathan Pryce, and Saskia Reeves. I might have missed some.
Eugene Levy and Catherine O’Hara have been in a bunch of stuff together, starting back at SCTV in the late 70s. I absolutely adored Schitt’s Creek; they are both brilliant in it.
John Banner and Werner Klemperer, of “Hogan’s Heroes” appeared together on “Alfred Hitchcock Presents” S1 E22 “Safe Conduct.”
Allison Janney and Bradley Whitford worked together on The West Wing and now on The Diplomat.
Played by Karl Urban as I recall.
How did she escape that one with her head?
Getting off-topic, but if anyone wants a Xena thread, I’d be happy to start one.
Smuggler’s Bay, a 6-part adaptation of the classic adventure novel Moonfleet starred Frazier Hines and Patrick Troughton.
Years later they would co-star as Doctor Who and Jamie.
Allyson Hannigan and Seth Green (Willow and Oz on Buffy) were both in My Stepmother Is An Alien (and in fact, their characters went on a precocious date together)