The animation is lovely first of all. Every frame is hand drawn and beautiful and I love how it's composited with the lighting. Just great work through and through. Like I don't even have words it just made my eyes cream for 20 minutes straight.
The story was okay. Nothing really changes in the characters by the end. I mean, Clay teaches the mouse fellow to stand up for himself by lashing out in a dickish fashion. But that didn't feel great to me.
The girl Clay sat across from could've had more significance. Like maybe he's beating himself up for screwing up talking to her, then he comes back when he's inebriated and she's amused a bit and then he can be like "oh my god I hate people but I might've made a friend???" and then he gets to leave the club a little uplifted. But he's not certain that they're friends and that's something you could develop in a future episode.
And then maybe the mouse guy follows the girls being their coat rack and is disturbed by the horrors of the popular kids being dicks or something and leaves a bit put off (maybe you can work in the pushover thing too)
And then you end the episode with Clay having enjoyed his experience and the mouse guy not and it's like a little y'know subversive thing and the characters have changed a bit through their experiences.
So yeah that's my Catching Up fanfiction.