ABC’s of idioms

Carrie and I sometimes play games that other people might find annoying or stupid, but we like them. Especially for long flights, inventing little games is a fun activity.
We decided this time, from Houston to Costa Rica, to invent the game “ABC’s of idioms”
(* represents one that we think isn’t really an idiom, but couldn’t come up with something else during our flight.)

All hands on Deck
Bite the bullet
Catch the flu
Don’t fly off the handle
Elephants never forget
Fit as a fiddle
Green behind the ears
Happy go lucky
Ignorance is bliss*
Jack in the box / Jam packed
Keep your head up
Lying through your teeth
Money doesn’t grow on trees
Over the hill
Penny pincher
Quiet as a mouse
Robbing Peter to pay Paul
Stitch in time saves nine
Ticking time bomb
Underwear in a bunch
Virtual reality *
Water under the bridge / wag the dog
X
Y
Z
What do you think? Are our * items idioms?
Can you think of idioms for X, Y, and Z?