Freshen Drains with Baking Soda and Vinegar
Baking soda and vinager, baking soda down first, followed by vinager then cover the drain to force the mix into the drain.
Or, now that the cat is fed, a pipe snake...it’s a tool not an animal.
If you need to snake the drain, here's a good tutorial: https://www.youtube.com/watch?v=P1LIlcZO94o
I would add to Alice's advice that you should cover the drain after adding the vinegar. I boil water rather than running hot tap water. You may have to repeat a couple of times.