According to Wikipedia, some versions have "cheese" instead of "malt".
Wikipedia gives what it describes as "perhaps the most common set of modern lyrics:
This is the house that Jack built.
This is the malt that lay in the house that Jack built.
This is the rat that ate the malt
That lay in the house that Jack built.
This is the cat that killed the rat ..."
... and so on. The cat was worried by a dog, the dog was tossed by a cow with a crumpled horn, ... and so on.
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