This one started off with three lines that appeared to me in a vision one day:
for they found Teresa
in dum-de-dums freezer
in convenient, family-sized joints
It took me ten years to construct the rest of the poem around them.
Incidentally, around the same time, I came up with this fragment, in a similar rhythm:
… I finally met Mr Big:
he was in a jacuzzi,
stroking an Uzi
and a Vietnamese pot-bellied pig
This is still defying my attempts to complete it, which may be no bad thing.