When the gopher eats all of the vegetables in Donald's garden. It wouldn't have been possible for the gopher to overeat all of the vegetables as it would've made him sick and throw up the food. It's possible that he had his gopher friends eat Donald's vegetables. But's it's unknown if his gopher friends invaded the garden underground or just pulled the vegetables underground to save for later.
When the gopher eats the onion he immediately rejects it. But at the end of the cartoon he just eats all of the vegetables despite his dislike for onions.
The Gopher depicted in this cartoon actually has an eating disorder and he would not been happy at the end but would actually feel very sick and unhappy and would have throw up, he would also get overweight. Unless he had his gopher friends underground help him eat the vegetables in the garden he would've not been able to finish off all the vegetables in Donald's garden and it would've taken him many days and the vegetables would rot by the time he got around to finishing the vegetables in the garden.
After Donald Duck gets tied down with watermelon vines by the gopher. The gopher eats all of the vegetables. It's unknown if Donald Duck ever got free from the watermelon vines that tied his body down. Or if one of his friends ever rescued him. Also the gopher never gets caught for the crime of stealing Donald's food and Binge eating, or paying for the damages he caused to Donald's Garden including replanting the garden or being caged up as punishment for stealing.