How it works on an indie cast
A producer has a $900,000 feature with five supporting roles, all shot under a SAG-AFTRA low-budget agreement. The offer to each actor is the same: a flat fee above scale for the run of the show, a shared cast trailer, and "favored nations with all supporting cast" for fee, per diem, and dressing room.
Three weeks later, a bigger-name actor's agent says their client will do the fifth role for $10,000 more. If the producer agrees, the other four supporting actors' fees go up by the same amount, because their deals promised nothing less favorable than anyone else in that group. That's $40,000 more on top of the one actor's bump, which is often the reason a producer says no.
Where the wording matters
The clause's reach comes down to two questions: who is in the comparison group, and which terms are covered. "Favored nations with the other series regulars" is narrower than "favored nations with all cast." "Fee and credit" is narrower than "all terms." A casting director and the production's attorney should agree on the language before offers go out, because once an early actor signs, every later deal in that group has to respect it.
The clause also works in more than one direction. A location owner might ask for favored nations with other properties used on the same street, so if a neighbor negotiates a higher fee, they get it too.
Mistakes producers make
Promising favored nations on perks the production can't deliver equally. If the lead has a private trailer and the supporting cast have favored nations on dressing rooms "with all cast," the producer has a problem.
Forgetting it's in the deal. A line producer approves a per diem bump for one actor on a distant location, and the payroll company isn't told that four other actors are owed the same thing.
Mixing favored nations and pay-or-play without thinking through the consequences. If one actor gets a pay-or-play guarantee and others have favored nations on "all terms," the others may be owed the guarantee too.
Where it shows up in paperwork
The clause lives in the cast deal memo or long-form agreement, and it should be flagged in whatever summary the production accountant and 2nd AD work from. Union agreements set minimums, like union scale, but favored nations is a private contract term layered on top.