The idea that God was so bored out of his mind he spent 6 days creating everything in the Universe, and for good measure put in several jokes to fool us into believing it must have taken him much longer.
According to this theory, He created everything in media res, ie, right in the middle of the action. Although the Universe is only 6000 years old, we see light from stars which appears to have taken billions of years to reach Earth. Although radioactive minerals in rocks appears to have taken billions of years to decay to the state we see in nature, the rocks are really only 6000 years old.
This is because God is really really sneaky. Basically, an omnipotent being can make a Universe any way He wants. He can make it so that everyone chooses of their own free will to be good; and evil and suffering don't exist. He can teach each and every human soul to reach salvation, no matter how long it takes (He's got all the time in the Universe and more if He wants it.)
But, according to Creationism, that's not what God did. Instead, He made malaria, elephantiasis, and bone-break fever. The theory of Creationism implies that a perfect, benevolent, all-powerful Being created a Universe which He knew would produce not only Jeffery Dahmer but The Backstreet Boys as well.
Needless to say, Creationism is highly regarded because it is almost perfectly illogical and incomprehensible -- harder to make sense of than Einstein's general relativity, quantum mechanics, and Keynesian economics combined. Something this nutty just has to be true.
On the other hand, some hold that Creationism has fallen into disrepute and has been called by renowned scientists across the globe: "A disease of the mind, in the same family as coprophilia, necrophilia, Gonorrhea Lectim, and fret wanking".
It may also be possible that the Universe is a cosmic soap opera for a Supremely bored God.