Quoting:

"A coffee cup and a doughnut are homeomorphic because a coffee cup can be stretched into a doughnut. A doughnut cannot be a sphere because a sphere does not have any holes. Cutting is not allowed in topology but Homer finds a workaround by biting the doughnut, because if you bite the top off of an A and eat it, then the top no longer exists. Homer makes the doughnut and the sphere homeomorphic. And maybe that’s why he’s also called Homer."