The cartoon animal could be crying because it didn't get what it wanted, or it's facing some kind of danger. There are many possible reasons.
It might be crying because its home was destroyed or it failed to achieve a goal. Different scenarios could lead to its tears.
Maybe it lost its friend or got hurt. Who knows?
It's popular because it often conveys emotions in a cute and relatable way. People can easily connect with the expressions of the animals.
You can start by sketching the basic shape of the animal. Then, add the details of the eyes and tears. Make the expression look sad and genuine.
Maybe it's because they want to evoke emotions and make people feel sympathetic.
Maybe the kid is sad because they lost their favorite toy.
Maybe he lost something precious or faced a big disappointment.
Maybe she's sad because she lost something important to her.
There could be various reasons. Maybe the kid failed a test at school, or he saw something scary. It all depends on the context of the cartoon.
Maybe he's sad because he lost something important to him.
Maybe it's sad because it lost its toy or got into a fight with another cat.
The girl might be crying because she failed at something important or received bad news. Or it could just be a part of the story's emotional plot.