OK, so in the series, we've been shown on multiple occasions that time travel is possible, and frequently used. My proposition to you all:

Baby Kal'El is transported through time and space via a wormhole. He hits his intended target (Earth) but he has travelled back in time, say, a couple hundred years (or whatever number you choose) to Smallville, KS, 1966 (as in canon). Jor'El and Lara, unaware of this time change they would be sending their son through, leave Clark under the impression (through use of the globe) that Krypton has exploded and he is the last of his kind. In reality, at the time when Clark is living, Krypton is still very much alive and prosperous, but still set up for a doomed fate in the future. (This theory obviously would have to dismiss the NK arc.) Suppose Clark discovers this anomaly, what would he do? Would he abandon earth to go save his people? Would he create a paradox where he was never sent to earth in the first place if Krypton was saved, or would he risk earth's utopia?

/waits patiently for someone to bite.../ I've got way too many ideas to follow and things to do for me to indulge this one... so I'd really like to see someone else tackle this.

Ooooh. I love this idea! Yes, very paradoxical, which of course would lead to inner turmoil inside of Clark. My favorite kind.

Yes, NK arc wouldn't make much sense, since Zara wouldn't have yet been born to make such a match. A new colony of Kryptonians is always possible though.

Perhaps baby Kal-El hasn't gone so very far back into the past, only far enough back for him to be a grown Superman on Earth (maybe even married to Lois, possibly with children of his own) when Jor-El's probes discover the planet. It is Jor-El who uncovers the anomaly and asks Superman to help save Krypton, and his and Lara's unborn child.

I'd read this if someone picked up this plot, but I'm currenly waist deep in another time-travel, dimension hopping saga.

Yes, was considering this. Like sort of a way for Clark to realize that Krypton hasn't exploded yet and why the heck is he here if that's not the case. (I'm imagining a sort of "I'm Kal'El"/"Who the heck are the Els?" kind of encounter :p ) But it would get too complicated until you said this:
That would be crazy!! Crazy good, of course. :p Now I definitely want someone to write this!

I don't have a response to your challenge, but it made me think of a nifty variant of it. Suppose Kal-El traveled much further back in time -- perhaps to one of the times depicted in Soul Mates, or perhaps some other time.

Would the Kents still raise him? If not them, then who? What would he become? If he traveled to a Soul Mates time, how would he and his Terran counterpart get along? How would Lois choose between his two instantiations?

Joy,
Lynn

Another variation is that we could just have The Fox or the Lone Rider be the result of a Kryptonian landing on earth. Hmm, although then they would be super-powered, unless of course something makes it so at that point the Superpowers don't kick in.

Stick with the original premise and ignore what the series said. It would be interesting to see the results of someone's muse working on this particular scenario.

I can't do this already in the midst of writing The Globe and Airport. So there is no way for me to stop my fics and work on this very interesting idea!