As mentioned previously, some players maintain the distinction between player knowledge and character knowledge very faithfully. But if you're clever, there will arise certain situations in which you can do something completely in character, that makes perfect sense without the player knowledge, and which forces the issue into the open.

If you pull this off, though, there is the strong temptation to do some out-of-character crowing.

Transcript

Obi-Wan: Is everyone in this party insane? We can't bargain the lives of innocent humans on this!
R2-D2: Yeah we can.
Obi-Wan: Queen Amidala is their leader. It's up to her.
Queen Amidala: I... er...
Qui-Gon: I'll decide. 1-3: we don't bargain with human lives—
Padmé: {stepping forward} Great Boss Nass. I am the real Queen Amidala.
Padmé: This is my loyal decoy.
Qui-Gon: I rolled a 17.
Qui-Gon: Wait... What?!
Obi-Wan: Aha! I knew it.
R2-D2: You knew?? Why didn't you tell us?
Obi-Wan: I knew, but Obi-Wan didn't.
{beat}
Qui-Gon: I don't follow.
R2-D2: So... you don't follow or Qui-Gon doesn't follow?
{beat panel: Qui-Gon really confused}