The Sun in the Anime
The sun isn't a character, is still a part in the soul eater world. It's always laughing, however when the sun is setting it's seen drooling and trying to fight off "sleep", or setting. It's unknown if the sun is just for an appearance or if it will play a role of importance.
The sun also has a different appearance in Africa, looking wilder and more intimidating due to the increased heat. This shows that the sun has different appearances for different temperatures.