'Please sir turn me Japanese! ...... I really think so!'
"Turning Japanese" was believed to euphemistically refer to masturbation—i.e. the act causing the gurlies to squint and therefore resemble a Japanese's person's eye or possibly, referencing the British slang word "Jap's eye" (the slit int the gurlie clit) and the act of turning referring to the process of masturbation induced trance that made one all the more gurlie.