Okay, I admit having laughed a bit, but in this case, I completely agree with Ovelix.
I am a catholic, and I find this 'humour' completely out of place. I wouldn't like seeing the same joke applied to Catholics (or Christians in general, or Jews...), it is just a proof of disrespect.
As Ovelix said, prayer is a sacred act. It is for Muslims, it is for Christians. If it is not for you, please respect it.
Okay, and now to lighten a bit, here is a joke about religion I like, because it doesn't attack the sacred aspect of it :
A Catholic priest and a rabbi were walking on a street when they saw a young boy.
"Come on, : said the priest. "Let's screw him"
"Okay, " said the rabbi "but out of what"
Antoine, Catholic with a Jewish grandmother