I love it! The animation, the sounds, the music... everything! It's always good to see fun, wacky, cat-and-mouse cartoons like this. It reminds me that you don't need to write a heavy-hearted and ham-fisted cartoon (like some of Steven Universe) in order to garner massive praise; sometimes, tried-and-true formulas like this are the most genuine ways to go.
Like I said before, the music is good, but if I had to nitpick, I would've turned it down just a little. Also, I would've tried to go with a more "consistent" and "authentic" sound. Doing this, I feel like it would've sounded more like someone playing a real piano and less like someone creating a track in FL Studio with piano "keys" peaking everywhere. I also would've added more (and changed a couple of) sound effects, but that's just me.
As a side note, I thought the ending was gonna be different. The first time watching this, with the way the cartoon was going, I anticipated something horrible happening to the cat lady. I imagined her about to be swarmed and consumed by millions of mosquitoes as the lights dimmed (much like that scene from 'The Mummy' where Beni gets eaten by scarabs), only to awaken from this nightmare by a sudden cold sweat and a few relatively inconsequential (but still really annoying) bites.
In short: it's one of the most satisfying cartoons I've seen in a while. Always looking forward to more of your work!