Cliché: can't make a silk purse out of a sow's ear

Meaning: can’t make something lovely out of something ugly
Rewrite 1: can’t make a silk purse out of an elephant’s ear
Rewrite 2: can’t make a T-bone out of stew meat
Rewrite 3: can’t turn a hovel into a mansion
Rewrite 4: can’t turn slop³ into cheesecake

Comment: Although there are plenty of ugly things and lots of lovely things, they can't all be related into a metaphor like this. The original comparison had a rural quality to it that can be limiting for some writers. To preserve that quality, the fourth rewrite might be better with something more like "can't turn slop into cake" or "can't turn slop into meat loaf."

More reading about clichés
What I found when I googled “clichés”
• The Movie Clichés List by Giancarlo Cairella. Lots of different categories of movie clichés, like airplanes, alcohol, and nightmares.

From a reader of this blog (thanks for the plug on Twitter!)(Updated 11.11.09)

• See The Loco Diner for reuse of this cliche. Nicely written.