Small Casts, Multiple Roles

In a standard Hollywood movie, every character has one role, and there are as many characters as there are roles to fill. In an action movie, there is the hero, the hero's friend/partner, the love interest, the bad guy, the bad guy's main lackey, and so forth. Every one of them is a distinct person.

The only time this changes is when the friend/partner was actually the bad guy all along. And that is such a tired twist that I would not really count it anymore.

This build has a purpose; it allows you to make a simple, straightforward story about two-dimensional characters (I say two-dimensional because the hero has to get the girl AND save the day). For Hollywood movies, it gets the job done. Usually, though, they get old real fast when you know the formula.

When you start making your cast of characters smaller, and you start having multiple roles filled by each character, stories get more interesting. Consider what happens when the love interest is also the bad guy's lackey, and that character having to deal with the conflicts of interest. And to make matters worse, the hero's partner is the love interest's ex boyfriend. Also, the hero killed the love interest's father in order to get to the bad guy. Now we have a complex web of relations that will make for a much more delicate or explosive story.

Small casts allow for a much deeper complexity in characters. The only real downside is that it makes you feel like it is a small world. The same seven people are somehow always related to what's going on, so it may be surprising, but when it gets overdone, it just becomes ridiculous. In fact, the one nice thing about a large cast is that it makes you feel like there is a large world.

Both styles have strengths and weaknesses. Use the one that does what you're looking for.