system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: During opening credits of a tv show, all of the actors and actresses names appear at the bottom of the screen but the last person getting the credit gets a special "Derp McDerpison as Steve" credit. Why is that?
gpt
Contracts. If given the choice, all the actors would want more money for appearing in a show. The unions generally set the pay scale, so more money is out. The next thing the actor wants is more work. More work means more money. The easiest way to get more work is to have more people know your name. So an actor would like to have his name fill the entire screen during the opening credits, but, again, union rules prohibit this. 

The next best thing an actor could get is to have his name listed first on the credits. There aren't any hard rules about the order of the names listed, so everybody figures the biggest star is first. And sometimes it is. But then you get a lot of people fighting to have their name listed first for an ensemble cast. Even if you could list everybody at the same time, the top honor position would be the top right position. 

So what producers decided to do is add something special for the guy who's name is listed last. Usually you want a big name, and they producer will have something special about that name. For example, Derp McDerpison as Steve, or Featuring Derp McDerpison. Or even, With a special guest appearance by Derp McDerpson as Steve. 

In short, it is just a way to make the cast members happy.