Carl is outside in his boxers trying to get his girlfriend’s cat out of a tree when everything with a roof on the planet is destroyed and the smaller number of survivors are made to compete in an intergalactic dungeon game similar to D&D. If this sounds kind of dumb, I described it correctly; it’s kind of dumb. It’s also fairly entertaining and has a good amount of heart. People who have played any sort of role playing game, like World Of Warcraft, will probably be extra amused.
It's a fairly early spoiler, but still a spoiler
The cat goes into the dungeon with him, and is initially treated as a pet. Pretty quickly, though, the cat gets an upgrade that turns her into her own character, and they become something of an iconic duo.
Also, I don’t know that I’d necessarily call it sci-fi, maybe more fantasy with… well. it’s complicated. In any case, I enjoyed it, and the rest of the series and highly recommend it.