I'm pretty sure I've recounted the following before but good enough to repeat.
There was a rather larger than life and physically large and pompous lecturer in university who answered the door in his string vest and braces, rather like Rab C Nesbit. "We'd like to talk to you about Jehovah". "Oh, you silly little man, I AM JEHOVAH!". The poor JW ran away.
(To be fair I have heard another version of the first story where the conversation goes "We're collecting for Jehovah" "I am Jehovah, how much have we got" attributed to an unrelated academic)
This next one is true. Some JW types called at a friend's place and she was politely trying to fob them off saying she was just going out and there was no one else home, when a load shout came from her boyfriend in the back room "Tell 'em to fark off"