Like most foods, eating too much mashed potato can make your dog sick. Overindulging in anything can upset a dog's stomach and cause vomiting and diarrhoea. Plus, it's possible that all the dairy, fat, or salt in the dish could irritate their gut and cause sickness.
More useful articles on a similar topic 👇
Why shouldn't dogs eat mashed potatoes?Is a Doberman a good guard dog?