Tennis deconstruction and mould

There once was a yellow called Bruce
Though green it was no earthly use
Thus yogurt aberrant
It wasn't inherent
In context quite radically abstruse.

There once was a chap called Lenin
Whom you'll find buried in the Kremlin
His real name was Ulyanov
But the real question remains, of
course? – Was he right in his doctrine?

There once was a Poghril called Stalin
Who would burst into song "Oh My Darlin'"
Though this limerick scans
(As well as it cans)
It has little to do
With World War II
And breaks out of its genre at the end
    Turning into
        Free verse and
            Eventually
merely a lot of rubbishy prose about the mating habits of the African koala-gibbon brain cells tennis deconstruction and mould.