Green’s Dictionary of Slang

(orig. US) an excl. of approval, of agreement, of surprise.

1952		T. Southern ‘The Night the Bird Blew for Doctor Warner’ in Southern (1973) 50: When a sleepy-faced drummer passed him a sweet cigarette, the thinness of two matchsticks, to hold it as he might have been expected, take quick deep drags [...] and say in a low voice, ‘Crazy, man’.
1965		(con. 1940s) Malcolm X Autobiog. (1968) 187: ‘My man!’ ‘Crazy, Red!’.
1979		H.C. Collins Street Gangs 222: Crazy Very good, I like it.
1994		Eble Campus Sl. Apr. 3: crazy – remarkable – ‘Bill burnt up my couch with his cigar.’ ‘Crazy.’.
2000		N. Barlay Crumple Zone 103: He’s set himself up as a pimp in Chinatown and says he’s gonna take Bayswater back from the Colombians. — Cray-zee, goes Jodie pretty uncertainly.