Reecently there seems to have been an explosion of expressions like the one above: “Stairs don’t reach the attic”, “a sandwich short of a picnic”, “not got all his oars in the water” etc.  Is it just me or are most of these recent coinages?  If so, when did the explosion start?

It looks like some versions of these run back to the 19th century, and may have gotten started in Australia.  See the OED excerpt (and request for submissions) here.

There was a spate if these back in the early 80s as well, many of which became popular and well known enough to be picked up by copy writers for radio commercials.

Well, since they seem to have originated in Australia, was that perhaps Barry Humphries, along with his colourful expressions for vomiting due to inebriation etc?

Bayard, I think he was a couple of cards short of a full deck. Err...just kidding.

And sometimes you don’t have to be short of anything....you can, for example, “have kangaroos in the top paddock”. See this entry in Urban Dictionary.

I don’t know about any of you, but I’m two spankings shy of a slap on the ass.