It could be because the creator wanted to highlight something unusual or create a memorable character. Or it might be part of a story with a special meaning related to sleep or a particular trait of the girl.
It could be that the car ride is super boring and made her fall asleep and snore. Or she might have had a late night before and is catching up on sleep now.
Maybe she's just really tired and having a deep sleep. That can happen to anyone, even in a cartoon!
I knew a girl who snored. Her best friend, who shared a room with her during a trip, found her snoring endearing. The friend would tell her in the morning how she was like a little sleeping bear, and they would laugh together. This simple acceptance made their friendship even stronger.
Maybe the dog is just really tired and needs some good rest, so it's snoring.
Maybe she's really tired and needs a good rest. That could cause her to snore.
It could be that the cartoon man has a blocked nose or is in an uncomfortable position, causing him to snore. Or perhaps he had a busy day and is now sleeping soundly and snoring as a result.
Maybe the cat is just really tired and in a deep sleep. That can cause it to snore.
Well, I once knew a girl who snored so loudly during a camping trip that it scared away the small animals nearby. It was quite hilarious.
It could be because a snoring dog makes for an interesting and unique character. It might attract kids' attention and bring some lightheartedness to the story.
The exaggerated expressions and sounds usually do the trick. Maybe a character's face contorting while snoring loudly can be hilarious.