About 15 to 20 years ago I watched a TV cartoon series (probably an anime) about a school boy who was living together with some alien (I think it was an alien, but I do not know its origin; maybe a deamon?). I am not sure whether the boy considered them friends, because the alien regularly used his various supernatural/reality bending abilities to annoy the boy and make his life harder. If I remember correctly, then this was not the obvious intention of the alien, but it seemed to be more like a result of it badly understanding the human nature.
If I remember correct, the alien went to school with the boy and the boy's family and friends knew the alien and considered it as nice. More generally, it seems noone else noticed the "suffering" of the boy.
I believe that the alien had some recognizable name, and that the series was named after it.
Here is a rough sketch of what I recall of the alien's face (it might be quite off though). It had otherwise human anatomy, and was appoximately as tall as the boy. Usually it had a neutral expression on its face. It was able to talk.
I watched it on German TV (thus, with German dub), most likely RTL II, but I do not remember.
A scene that I remember
I remember the following scene from one of the episodes.
The alien, the boy and some friends are stranded on a small rubber boat on the ocean. At some point the alien steps out of the boat and it turns out that the water is very shallow as the allien's legs only go in ankledeep. So the boy is relieved and also climbs out of the boat, immediately plunging into deep water. As the boy struggles to get back to the surface he sees that the alien just extended his legs to reach to the ocean's floor.