A little trick for the day: When improvising something, think about a normal thing and then bring to it a little twist. "You get to the show, almost too late. The magician is at the end of his show. He shows to the audience the hat, which is empty of course, and then he puts it on the table and his hand circles all around the hat. When he pulls it out of the hat, there's a lion's mouth held in his hand. He raises the hand, 'till the entire lion is out..." Not spectacular, just a normal magic trick, 'till the magician pulls not a rabbit or a bird out of the hat but a living lion. In a moment, with a little addition, we have a unique magician with a unique magic trick.
It can be used, of course, to more than just portraying NPCs. It can be used to paint the scenery (the clouds look like tears, only painted green"), to make a building stand out ("The west wall has 43 windows in different sizes"), or even to pitch a game ("it's like Star Wars, only you play a group of Chubakas...").