It could be part of a funny story or a crazy adventure. Maybe they were looking for something hidden down there.
The cartoon man could be digging a hole to build a foundation for a new structure. Or it might be part of a treasure hunt. There are various possibilities.
Maybe he's looking for something buried. That could be treasure or an important item.
Maybe he's just being mischievous or trying to cause some kind of effect. It's hard to say for sure without more context.
Maybe it's part of the cartoon's unique design or for some symbolic reason.
Maybe it's because the idea wasn't popular or didn't fit the theme of the cartoons being made.
It could be that the boomerang was a special possession passed down to him, or he found it and thought it would be useful for various tasks in the hole.
Maybe he's digging to plant a tree or build something.
Maybe he's looking for treasure buried underground.
Maybe he's playing a game of hide and seek and thinks the hole is a great hiding spot.
Maybe it's curious about what's inside. Sometimes characters do strange things out of curiosity.