The statement "Boy, it's a madhouse in there is an example of a self-reference opener.
In a sentence context, a self-reference style usually represents a statement that refers to its own self or it serves as its own subject.
From the given statement, the boy is referring to the audience about himself being his own subject while talking about what he witnessed in the house. i.e.
Therefore, the statement "Boy, it's a madhouse in there is an example of a self-reference opener.
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