Are the thoughts that come to mind with mockery of people and cause laughter sinful, and are they from Satan?

There is no sin in this matter as long as you strive against yourself to turn away from it and have not spoken of it. You should seek refuge with Allah from Satan, for Allah Almighty says: "And if an evil whisper from Satan reaches you, then seek refuge with Allah. Verily, He is the All-Hearer, the All-Knower." And occupy yourself with learning and fruitful work, rather than thinking about these matters.