Sometimes celebrity drawings are a kind of 'fan art', drawn in homage to our celebrity idols. But often they are caught in character or at a particular moment that expresses something more universal. Their images become iconic, as in this portrait of Hendrix drawn by Lulu Pelletier.
If you're drawing a celebrity portrait for public display, make sure you choose a public-domain reference source, and don't use images which are copyrighted by photographers, magazines or movie companies.
Go to the Celebrity Portrait Drawing Art Gallery.