The second dog answers, "I have an incontinence problem. I think I'm here to be put down. What about you?".

"Well, I spend all day digging up my owners garden and I think I'm here to be put down too."

They both turn to the third dog and ask what he's there for.

He looked a bit sheepish and replied, "My mistress likes to do her house work in the nude. Well, one morning she was on her hands and knees washing the kitchen floor. So I crept up behind her and showed her why we have our own style."

"Holy shit!" said the first dog. "You must be here to be put down too?"

The third dog then grinned and said, "No, I'm here to have my nails clipped."

Thanks to Greg for the great joke.