David Manders <email@example.com> asks:
> How, in general, are the 'frequent irregulars' contracted, and
> how are their parts shot? Are they contracted to be 'on call' or
> are all their scenes for a series shot in one set of sessions, or
> perhaps a mixture of both?
You contract with an actor for 8, 13, 18 or 22 episodes. You
then use them for those episodes within a given period of time.