ER, Season 6

Vanilla Latte Boy (to Luka):
I don't get this. You're a regular doctor...

Luka:
Yes.

Vanilla Latte Boy:
...But you don't work here.

Luka:
No, I do work here, but only when they need me. I'm what they call a "Moonlighter."

Vanilla Latte Boy:
Because you're from another country?

Luka:
No, because I only work here from time to time, when they need me.

Vanilla Latte Boy:
And they needed you today because of the truck crash!

Luka:
(sighs) No. I'm here because one of the regular doctors...

Vanilla Latte Boy:
I thought you said you were one of the regular doctors.

Luka:
I just fill in when someone else is absent.

Vanilla Latte Boy:
Oh, I get it! You're like a sub!

Luka:
A sub...? Yeah, yeah. I'm a sub.

Vanilla Latte Boy:
What kind of accent is that?

Luka:
(sighs again) Thick!