A Universal Truth

The following idea can be applied to absolutely any cast of characters.  It has yet to be proven wrong.

When writing or telling a story, consider this.  Every group consists of:

The leader
The optimist
The aggressive pacifist
The troubled one

But here's the cool part:

The leader, who is best friends with the optimist, has some sort of drama with the troubled one, but the aggressive pacifist acts as a mediator between the two.

Example: Star Wars 

The leader- Luke Skywalker
The optimist- C-3PO and R2D2
The aggressive pacifist- Princess Leia
The troubled one- Han Solo

Luke leads the group (rescues Leia and blows up the Death Star).  R2 (grouped with 3PO) is his most loyal companion.  Luke clashes with Han, while Leia not only mediates between them personally, but also physically (she loves Han, but is Luke's sister).

But here's where it gets freaky: 

Example: Friends (the TV show)

The leader- Chandler and Monica
The optimist- Joey
The aggressive pacifist- Phoebe
The troubled one- Ross and Rachael

Chandler and Monica are the model couple, being happily married.  Joey is Chandler's best friend.  Ross and Rachael sharply contrast Chandler and Monica (substituting for drama (the one after Chandler proposes?)), while Phoebe, who usually settles the big fights, mediates between both couples.

Try it out.  Any character can be put anywhere here, sometimes even more than once!