The "Fenian boys" version also has accreted:

Mary had a little lamb.
It had a sooty foot.
And everywhere that Mary went,
Its sooty foot it put.

Mary had a little lamb.
Her father shot it dead.
Now Mary takes the lamb to school
Between two hunks of bread.

Some other naughty-schoolboy verses I heard as a naughty schoolboy:

Mary had a little lamb.
She tied it to the heater,
And every time it turned around,
It burned its little peter.

Mary had a little lamb.
She tied it to the sink,
And every time it turned around,
It froze its little dink.