I remember this one from a Warner Brothers cartoon. The third line is:
Man:“Who was the greatest baseball player of all time”
Dog:“Ruth”
Bartender throws them out. Then the dog says to the man, “Maybe I should have said DiMaggio”.
The joke I am thinking of is very cloudy. Something about a man who has a purebred dog who he is trying to use for breeding, but never will have sex with any female dogs. The owner decides to get rid of him so he gives him a bone and $20 and sends him away. A little while later the dog is seen getting it on with a female dog in an alley. The ex-owner says “Rover, how come you never did this before?” and the dog replies “because I never had $20 before”.
I probably totally screwed that joke up.