Zachary Gray (spelled "Grey" in The Moon by Night, but "Gray" thereafter) is a fictional character in the young adult novels of Madeleine L'Engle. He appears in four novels, and is mentioned in at least one more.

Zachary, often called Zach, is a wealthy young man from Los Angeles, California, with parents who show little love for their son or each other, and who seem unable to exert any influence on their son's behavior. Zach is described as having "velvety black" hair, very pale skin, and "steel-grey" eyes. He is considered "gorgeous" by Vicky Austin and is taller than Polly O'Keefe, who considers herself "too tall." Intelligent but erratic in behavior, Zach is "kicked out" of numerous prestigious schools (namely for smoking in the bathroom or cheating as an art form), but demonstrates that he will learn a great deal on a subject that interests him, particularly anthropology. Zach suffers from a heart condition, and is often reckless and self-destructive, but at other times seeks desperately to live. Similarly, he is torn between cynical self-interest and more altruistic desires. Zach pursues relationships with L'Engle protagonists Vicky Austin and later Polly O'Keefe, apparently seeking emotional rescue. In his introductory appearance, he frequently sings "The Merry Minuet" by Sheldon Harnick, a song of black humor and global annihilation. Donald R. Hettinga says of Zachary at this stage that he "looks at human suffering and sees no hope." When his mother dies, he and his father have her body preserved through cryonics in lieu of a "pie in the sky" hope of resurrection. According to Carole F. Chase's study of L'Engle's work, L'Engle considered Zachary to be "a work in progress who will ultimately be redeemed."

Paper tiger is a literal English translation of the Chinese phrase zhǐlǎohǔ (simplified Chinese: 纸老虎; traditional Chinese: 紙老虎), meaning something that seems as threatening as a tiger, but is really harmless. This Chinese colloquialism is similar to the English phrase "its bark is worse than its bite".

The phrase is an ancient one in Chinese culture, but sources differ as to when it entered the English vocabulary. It is found translated to English as early as 1836, in a work by John Francis Davis.

In a 1956 interview with the American journalist Anna Louise Strong, Mao Zedong used the phrase to describe American imperialism:

In Mao Zedong's view, "all reactionaries are paper tigers" — superficially powerful but prone to overextension leading to sudden collapse. When Mao criticized Soviet "appeasement" of the United States during the Sino-Soviet split, Premier Nikita Khrushchev reportedly pointed out, "the paper tiger has nuclear teeth."

Osama bin Ladin used the phrase describing the American soldier: