Note, this only works if your church has a font
or something similar.
Once upon a time, I had a roommate. Now, my roommate was born Catholic. Fortunately or unfortunately for him, he didn't stay that way(eventually just building a shrine to Tori Amos and marshmallow peeps). The real problem was that his mother was strongly Catholic(and just plain strong) to the point of driving 20 minutes to pick him up at our apartment to make sure he went to church. Being a good friend, and after waiting for him utter the magic words "I wish I could do something so I didn't have to go to church", I sprang into action.
Rising early, I crept into his room with the stealth of an agnostic ninja. With great care, I gently dusted Alka-Seltzer between his fingers and under his nails, reset his alarm for about 2 minutes after his mom would arrive, and went back to my nest to wait.
Lo and behold, he was promptly returned not more than an hour later, his mother screeching about how she "always knew he was bad, but this...yaddda yadda yadda".    As I had planned, he hadn't noticed the dust(perhaps he thought it was chalk?) and had stuck his hand in some holy water in sight of a priest.
And for some reason, he never thanked me...