I don't find these funny because they're pranking Christians, before anyone gets offended. I find them funny because the hosts have no idea what's going on. There *are* puerile and offensive ones posted up on youtube, but you won't find them here. I haven't posted those ones because they're rubbish. THESE ones are genuinely funny, I believe.
However, that said, the funniest thing about the third one is the off-camera voice saying "No! No!" as soon as the host gets a few words in and the crew realise what's going on.
NOTE: I actually feared that I would have some kind of seizure after watching these, I was laughing so hard.
EDIT: I have just stopped laughing after about seven minutes.