'One or many' looks at collective agreements.
English verbs are usually rather simpler than in many other languages ~ but we still need to check we avoid using a plural verb with a singular subject, for instance. That may sound straightforward, but when the subject is a singular but Collective noun, many of us get 'interference' and put a plural verb after it.
You may be surprised how tricky it can be to get these right every time!
The cast of any show, meanwhile, is a collective entity, and therefore singular.