He's sly as a fox and crazy as a loon

John Prine - In Spite of Ourselves lyrics meaning

Meaning

"Sly as a fox" is an idiom for someone who is cunning and experienced; someone who can get what they want by any means necessary (sneaky and underhanded included).

"Crazy as a loon" is an idiom for someone who acts completely goofy or acts like the Mad Hatter of Alice in Wonderland.

Both of these are presented by the wife as left-handed compliments about her husband.

These "not quite sure they were compliments" are typical of older married people who've learned to appreciate the uniqueness of their spouse.

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