Criminal Sentence 48: Tricky Parentheses

When you have a period and some parentheses, how do you know whether the period goes inside or outside of the parenthesis?

Incorrect: I am making you dinner tonight (that's unusual.)
Correct: I am making you dinner tonight (that's unusual).
Correct: I am making you dinner tonight. (That's unusual.)

If the entire sentence is within parentheses, as in the last example, then you put the period inside. In any other circumstance, you put it outside. (Now you know.)