You've already broken my suspension of disbelief in your description of the alternate universe. A planet-wide catastrophe that results in a (more-or-less) permanent shroud of darkness is unlikely to result in giving everyone the "grimdark" treatment in terms of their personality. Depression and hoplessness will be the most likely result accross the board, as the world's ecosystems collapses, and likely taking much of large-scale human civilization with it. Mass starvation and death would then follow, as staple crops fail to grow in the same numbers as before. It won't make a genius a smart-aleck, and it won't make a comedian start wanting to pull dangerous and likely fatal pranks on others.
Humans just don't work like that. Unless the comedian was already a sociopath, they wouldn't start to think it's funny to actually go kill and maim others. In fact, under the circumstances, they may just decide to commit suicide (as there is a bit of a link between "funny people" and depression) since the world's gone to hell. Another comedian might decide that it's the best time to ply his trade, as people may want some respite, no matter how brief, from the constant warring/scavenging of daily life. A third may say "screw comedy!" and become a community organizer or a leader to help keep the wheels of society going.
If you are dead-set on your characterization of the alternate 'verse, then the apocalyptic event itself needs to be anomalous as well. Even then, you'd need to write this exceptionally well to pull off the whole "reduced to grimdark stereotypes" aspect.
