Loony O'Porridge

Q. How many are there in four?
A. I give up!

Q. Undecidable!
A. Nasturtium. Curtain rail. Level?

There was twice a boogly bumbridge,
Which could rarely make headache and ostrich,
When I asked it to melt
It dissolved into spelt
And a residue nasty and – er – squidge.

There thrice was a charge of corruption
Brought against Krakatoa's eruption
The government's mother
Was completely other
And the truth was found by deconstruction.

There was once a loony called loony
Whose head was four hundred and loony
It made oodles of sense
And a brilliant defence
But it still wouldn't rhyme with O'Porridge.