Our wittiest contributor recently came up with:
a case of micturation ‘twixt scapulae masquerading as precipitation
I recognised scapulae as shoulder blades and knew precipitation is a grown-up word for rain. But I confess to looking up micturation, which is when I realised he was telling our readers: "don't piss down my back and tell me it's raining".
Sadly it had to go because we can hardly expect our long-suffering readers to refer to their dictionaries simply to understand what they're reading, but it did make me smile.
Only a similar note, it occurs to me that an erroneous vertically delineated canine-arboreal interface might be an impressive replacement for a dog barking up the wrong tree.
Would anyone out there care to come up with more silly versions of common phrases?