A couple sees a classified ad for placing a "Christian dog" in a good home. "How," they wonder, "do the owners know the dog is Christian?" So they have to go check it out.
"Oh, yes," the owners say, "he's a good Christian dog. Watch this." They call the dog over and command, "Pray!"
The dog, of course, puts his head down on his paws and appears to be praying.
"Umm...okay, nice trick. But it doesn't prove he's Christian."
"Well, how about this? Fido, what will comfort me when I'm dying?"
The dog retrieves the family bible, then flips the pages to the 23rd Psalm, putting his paw over the verse that says, "Yea, though I walk through the valley of the shadow of death, I will fear no evil".
The couple is, naturally, impressed. They take the dog home.
A few days later, their pastor comes by to visit, and they're showing off the dog. The dog prays, the dog finds comforting verses in the Bible. The dog is, obviously, a Christian.
The pastor's wife timidly asks, "Does he do any...you know...normal dog tricks?"
"Well, let's see...Fido, roll over!"
The dog rolls over.
"Fido, shake hands!"
The dog goes to the pastor and offers his paw.
"Fido, heel!"
The dog goes to the pastor's wife and puts his paw on her forehead.
"Oh my goodness", remarks the pastor, "he's a Pentecostal dog!"