When you let a player know they can get away with more than they thought they could, there's going to be trouble. Pretty soon they'll be pushing against all sorts of limits to see what else they can get up to.

Better to keep them strictly limited in what they can do. Otherwise they might indulge in some roleplaying.

Transcript

Dex: What can I do for you?!
Obi-Wan: I have this poison dart. I was wondering if you could identify it.
GM: Sally, you don't—
Dex: It's from the planet Kamino! There are tall giraffe aliens there!
Obi-Wan: Kamino, huh? Do I know where that is?
GM: No. You've never heard of it.
Obi-Wan: Can you show me where that is, Dex? You could come with me and have fun adventures.
Dex: Oh, no. I have to run my diner.
GM: You really should go with Obi-Wan.
Dex: No no, and leave these roller-skate droids to run the place? I'd be ruined!
GM: But you have to—
Obi-Wan: In-character, she has a point.
GM: <sigh> Okay, fine.