Cats are adorable and quirky at the same time. They sometimes eat unusual things that can get us worried because there are many foods out there that are safe to humans, but not to cats. [Human foods that are Harmful to Cats]
Watermelon is not poisonous to cats, but its seeds can be and it has very little nutritional value. In fact, many types of nuts and seeds contain cyanogenic glycosides that is toxic to felines.
The Persian kitty from the video is loving her seedless watermelon snack, munching away.