The Azazel short stories by Isaac Asimov all followed a common theme: narrator would sit down for a drink with his friend, knowing full well that at a specific level of drunkeness he would begin to tell him a new story about this small demon-like creature he had exclusive access to. Azazel wasn't actually a demon, he was some kind of interdimensional alien life form, but he spoke English and delighted in using his powers to help out humans since, among his own people, he was considered something of a loser.
Anyways, this friend was verboten by Azazel to use his powers for his personal edification (no making large piles of gold or granting immortality); instead, Azazel would help out people he knew on the sly with whatever difficulties they were facing. The help was always well-intentioned, and would always go spectacularly wrong. The fun was in watching just how they would screw up.
One story, for instance, involved a very beautiful woman who came to Azazel's "master" for help in meeting men. Her looks and personality were winners, but she was upset because even a mild serving of alcohol would turn her into a complete fool. Azazel was consulted secretly for help, and after a quick briefing on the effect of alcohol on the human body and brain, Azazel announced he could change her body so that alcohol would be completely metabolized before it could cause intoxication.
Once the woman found out she was immune to drunkeness, she began "hanging out with the guys" at the bars on a daily basis. Then the nature of Azazel's boon became apparent: the alcohol, once metabolized by her body, was unused for any energy purposes and was thus quickly converted into fat. Enormous amounts of it. Needless to say, she wasn't terribly grateful.
This limerick was written by Asimov and published on the back of the dust jacket of the first "Azazel" story collection:
A small demon whose name is Azazel
Has magical powers that dazzle.
But those people who strive
To get them derive
Nothing much, and are beat to a frazzle.