Despite your ill intentions, I'd be ok with it. I'd fake you out with 'pain' from the cross.. but then reveal how such trinkets do me no harm. The garlic, however.. does sting a slight bit. Used to cause a terrible rash but the centuries have curbed that allergy. Now it's just irritating.
If I did a great acting job with the cross, appearing to melt and sizzle, would you like me when I jumped up, laughing and showing I was totally full of it?