Very nice. This was fun, and balanced well. I finished up with a full restaurant and kitchen. :) I loved the music. While it works as a short little game, I would love to see it fleshed out with more features, like building out the restaurant. filling out your menus with more options, skills for servers and cooks, customer opinion, critics.
I did move on from libGDX though, to Godot. Though not with this project, yet.
Regarding the animals, the question was how to differentiate the different customer types (each with different preferences). I know this form other games, where there would be teens, yuppies, old people, something like that. I never really liked that much, as the groups are not that easily differentiated and it was never intuitively clear which group might like what. With animals, that all works nicely :)