system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do some actors on TV get credited as "with", "featuring", or "and"?

For example, It's Always Sunny in Philadelphia (the only example that ever stays with me) stars Charlie Day, Glenn Howerton, Rob McElhenney...with Danny DeVito. What's the difference?
gpt
It's called last-billed. It's when you have an actor whose stature would normally put them at the front of the credits, but contractual obligations to another actor preclude that. While first is best, in the middle is worst -- so being billed last is a plus.