God wanted to make up a joke that would always make Him laugh, so He created the fart.
His Wife was disgusted by this, having to change the diapers for all of His creations and not finding such things humorous at all.
"Why did you invent the foul smelling wind from the buttox of Your creations? And why did You have it make such a horrible sound?" She would ask Him.
God shrugged and said "Cuz' I'm God, that's why."
Later that night, God's wife woke up after Her Husband was asleep and ate chili beans, brisket and cooked cauliflower. She then got back into bed and let loose the loudest, worst smelling fart of all time. One that was so loud and smelled so bad that it awoke God Himself from His sleep, gasping for breath.
And that was how the universe was created.