Imagine you are given the following scene:
A: Lets get out of here.
A: This place gives me the creeps.
B: Disneyland gives you the creeps.
You can tell off the bat that its comedy. If you were person B, you might deliver your final line with a bit more juice, a bit more volume because we know that punchlines have a certain underline to them, a certain "ta-da" factor. Thats great in most cases, and probably all you need. But if this is an audition, chances are the auditors have heard it delivered that way all day and so the effect may have worn off. This is where sincerity can save you and even make your hand out. Consider delivering the punchline as a concerned friend placing an understanding hand on A's shoulder and delivering your last line with all the sincerity of an intervention. Or consider delivering your last line as an eye-opening discovery that you just realized about person A.
Now look at the lines from person A's point of view. After being told that "Disneyland gives you the creeps," you might be tempted to give person B a disgusted look, maybe play into the fact that you are being ridiculed. But what are your other options? What if you were to play it as if Disneyland sincerely did give you the creeps, and what person B is saying is actually true? You might slowly nod in agreement after B ridicules you. You might even give a quick glance around the room as if Disneyland is somehow lurking in the shadows somewhere ready to scare you. All this comes from playing the sincerity of a comedic scene rather than the obvious sarcasm, and in my opinion, it will come off even funnier.
Best of luck out there friends. Let me know if there is anything I can do to help.