Use the following idioms as literally as possible without mentioning the original idiom, so "wet blanket" will include a real wet blanket. For Nano you may want to pick just one :-) For others, write a few sentences for as many as you can in 10 minutes, or use one and see where it takes you.
Cry over spilled milk.
Pull the wool over his eyes.
Wet behind the ears.
Wild goose chase.
Sky's the limit.
With flying colors.
Face the music.
Throw a monkey wrench into the works.
Can't make heads or tails out of it.
The pen is mightier than the sword.
Third time's the charm.
On cloud nine.
