Putting down a new lot and Disaster strikes!

[Hosfac]

So does that mean it's not random?

There are certain houses that seem to be far more likely to have one, but I've had it happen (very, very rarely) on various vacant lots as well.  I've also played on lots that I know it has happened regularly and not have it happen.  So there does appear to be some small degree of randomness to it.

[fortheloveofcake]

Does the message pop up before your sim has moved in, like when they are in the process of purchasing? Or is it once they are already on the lot?

[Sportsfan]

The message pops up after you have chosen the lot and choose start game, and then before the house and sims show up there is a pop up message that asks you if you want to accept the challenge.

[fortheloveofcake]

Hmm interesting... I'm determined to get one of these challenges so a lot of starting and restarting in my near future!

[Anushka]

I think it is fully random. I once had it in a world I built from a scratch, it happen while I was testing it.
In SV I got it in Mosquito Cove twice (but I almost always start from there if not from empty lot.
In BP I got it on small lot near the bridge, also a starter.
I'll make shore to better document them in future

[CreativeCrayola]

It's really not a big deal. I get it all the time, and it's a bit of a nuiscence. If it's the meteor challenge, there are the unremovable mucky marks everywhere, and I aways move after that.

[simfulicious]

The meteor one gives you some extra money from picking up the rocks, which can be helpful when you're a poor starting sim.  The garbage one usually has various forms of fruit laying around that give you a chance to start gardening for free.  I always say yes to these challenges because there is usually something of use for the sim, besides the extra work.