I worked at a Petsmart for two years. 3nodding
Started as a cashier for six months, later changed departments to Pet Care. My responsibilities were to, other than sell the animals and species-appropriate (HA!) kits and product, clean the cages/tanks, feed the critters, medicate/monitor new arrivals and ill animals, get the dead/dying fish out of the tanks, bag crickets and sell packaged bugs, receive shipments of both new critters and product, catch and box critters for customers buying them, and keep my department clean and orderly. Oh! And also to take care of the Adoption Center animals (cats only, in that location's case).
And occasionally help out the front during high-traffic sales days. (I hated that part; cashiering is not something I enjoyed doing because it was so darn repetitive. It's why I moved departments in the first place.)
Can't really tell you what the groomers' jobs are like, except from a retail drone's view of customer bitching. Busy, and with potential to get hollered at when Fifi's cut isn't what the customer wanted despite being the one they described, or if Spot decided to get a little nasty concerning his nails, or "Quit manhandling my dog!" when you put a fussy pooch on a shorter grooming table leash for your own safety. These are extreme examples, but they do happen same as their toned-down grumbly counterparts.
It's a little less wacko than food service, but like other retail experiences, has its ups and downs and psycho-nutty customers. But for every nutjob customer, there's a few good ones who'll give you praise either to your face or through surveys. So if you think you'd enjoy it despite me being kinda negative about it (different locations give different experiences), go for it! It really is a good experience in spite of the nasty customers and sometimes-less-than-favorable tasks. I'd do it again before I took up foodservice.