"A passing craze" is a short-lived trend or fad. It's something that is very fashionable or trendy and lots of people take part in it, but it passes quickly. If you're talking about technically grammatically correct English - no. "Ain't no" is not only a double negative but many people dislike the word "Ain't". It has the same grammatical problem as the Rolling Stones song "I Can't Get No Satisfaction". However, song lyrics make little attempt to be grammatically correct and "Hakuna Matata" is no different.
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