(informal) Indicates the suddenness of a change or transformation, as a magic trick in which one object appears to be suddenly transformed into another.
1929, Business Week, advertisement,
Just one touch lets you go from black to a second color. Presto. Chango. Or back to black. Presto. Chango. Color copies have never been easier.
1937 April 24, Washington Post, page 12,
PRESTO CHANGO! From a dreary, commonplace piece to a smart colorful chair shining with personality.
1978, Richard Rhodes, Holy Secrets, Doubleday, ISBN 0385025653, page 31,
"...An' presto-chango, you got yourself a twenty-eight-by-sixty-foot house."
1983, Lois Lowry, Taking Care of Terrific, Houghton Mifflin Children's Books, ISBN 0395340705, page 158,
Tom nodded solemnly. "Presto Chango," he said. Then he looked at the policeman again. "My name is Joshua Cameron," he announced, and the policeman wrote that down.
2000, Candace Sherk Savage, Witch: The Wild Ride from Wicked to Wicca, Sterling Publishing, ISBN 1550548786, page 8,
Watch and before your eyes, presto chango, a capital crime of the most hideous sort will be turned into a superstition,....