Maybe the dog sees the mailman as an intruder and is trying to protect its territory.
It could be that the dog is just being territorial and doesn't like strangers coming near. Or perhaps it's been trained to bark at delivery people. Another possibility is that the dog is excited and barking is its way of expressing that.
The dog might bark at the mailman in the cartoon because it's instinctively wary of strangers. Or maybe the dog is excited and just expressing itself in a way that seems like barking at the mailman.
Maybe it saw something that made it feel threatened or excited.
Maybe it saw something that made it excited or scared.
It could be barking to protect its territory or to get attention. Sometimes dogs bark just because they're excited or trying to communicate something.
Maybe it's for a fun costume party or to play a pretend game.
The cartoon dog might be looking at the mailman because it's expecting a treat or a package for its owner. Maybe it's just observing the daily routine out of boredom.
The dog could be looking at the mailman because it's guarding the house and is on alert. Or maybe it just recognizes the mailman and is observing. It could be for various reasons.
Maybe the dog is excited about going on a trip or is trying to get the attention of its owner.
Maybe the dog is excited or scared by something in the car.
Maybe the dog is excited or sees something interesting and is trying to communicate that through barking while being on the leash.