A man walks into the bar and notices a horse at one end with a hat full of money.  He asks the bartender what's up with the horse and money.  The bartender says, "Put $10 in that hat, and if you can make that horse laugh all they money is yours."  The man thinks for a bit and then goes up to the horse puts $10 in that hat and whispers into the horses ear.  The horse busts a gut laughing.  The man takes the money and leaves.  

Next week the man returns and sees the horse with a hat full of money by it.  He starts to go up to the horse to put his money in the hat and the bartender remembers him and says, "Oh no! You have to make the horse cry in order to win the money."  The man puts $10 in the hat and then leads the horse into the bathroom.  A minutes later the man is leading the horse out of the bathroom and the horse is sobbing.  The man takes the money from the hat and starts to leave.  The bartender stops him and wants to know how the man did it.  "How did you get that horse to laugh?" asks the bartender.  The man replies, "I whispered in his ear that my cock was bigger than his."  "Well how did you make the horse cry like that?"  "Easy," the man says, "I took him in tha bathroom and proved it!"