I think it would be a metaphor, because this phrase is probably being used to describe a person, not an actual snake.
Do you know how the phrase is being used?
If you are referring to this excerpt,
I heard you asking questions of each: Who killed the pork chops? What price bananas? Are you my Angel?
Then the reason is that it uses this structure to have a casual situation bringing the mood of the story to be light.
No, the phrase is just fine as it is