How can anyone confuse a baby kangaroo from Australia with a tiny American mouse?
It became a running joke in the course of 16 Hippety Hopper cartoons, produced between 1948-64. Hippety never had a short all to himself, although this next item bears his name. In it, a Brooklyn mouse, contemplating suicide, is saved by Hippety, and, perhaps unsurprisingly, the rodent also mistakes Hippety for one of his kin. I guess it's because they have the same skin color. Anyway, inevitably, the mouse takes Hippety home with him to confront Sylvester. You can guess the rest.
Hippety never spoke---he was a baby, after all---so everyone else had to carry the action for him. Some folks must wonder why Sylvester drew the short straw to get embarrassed by Hippety every time.