Dad told this joke on our ride to work

A king used to have a horse. He loved this horse of his, but the only problem was that the horse wouldn't stop crying. Ever.
One day the king announces that he will reward anyone who is able to stop the horse from crying. However, he would behead anyone who fails at it.
People from all over the kingdom show up: Jesters, people claiming to be horse whisperers, etc. and they all fail at it and get beheaded.
As the king was losing hope, one day, a skinny, poor man shows up, claiming that he could stop the horses crying. The king says "Alright, but remember: if you fail, you will be beheaded" The man nods his head, and approaches the horse, leans over to its ear, and whispers something.
The horse suddenly starts laughing uncontrollably. The king, cheerfully, asks the guy what he whispered. The man replies "I just told him that mine is bigger than his"
After receiving his reward, the man leaves. After a few days, the horse still wont stop laughing' so the king announces that there would be a prize for anyone who could stop the horse from laughing, and if they fail, they would get beheaded.
Many people show up again, and they all fail, and get beheaded. One day, the same poor man shows up, saying he could stop the horse from laughing, only if everyone else besides the horse leaves the room.
The king, confused, leaves the room with his guards. After a few seconds, they hear that the laughing has stopped, and the horse started crying again. They barge back in, and the king demands the man to tell him what he did to the horse.
The man, zipping up his pants, said "I just showed him that I was telling the truth last time I came"

(It was much funnier originally as I translated it from Turkish, so sorry if anyone has heard this joke before, and it seems like I butchered it :P)