A roos loose in the top paddock :

 

Someone a little crazy, mentally unstable.

My version of that was " A sandwich short of a picnic ".

Or A Sausage short of a barbecue :

Or - a slate is off and the water has got in

Or - the lights are on but nobody is home.

Or; A couple of Tinnies short of a slab :

Beauty is only skin deep, but ugly runs through to the bone.



Rodge (aka Twelvebore)

He's got an Awning over the toy shop:

 

 

male beer belly

 

Mow the Brigalo suckers :

 

shave the beard

One cup short of a tea set.

Make it idiot proof and someone will create a better idiot.

The gate is open but the beast is asleep

 

(Said to someone who's left their flies open)

If it ain't broke, fix it until it is.



It's life Jim, but not as WE know it.
Live long and prosper.

I couldn't repair your brakes, so I made your horn louder!

Couldn't pour water out of a boot if the instructions were printed on the heel.

Sixpence short of a shilling - a little bit dim

Gone Dolally tap tap - mad

'He couldn't tell a barn door from a bale of hay.'  or 'He couldn't tell a bull from a barn door.'  (A bit dangerous I would think.)