"Don't let the pants fool you"?

Question

What does it mean?

Answer 1

Probably that the wearer of the pants is more feminine than masculine in nature.  

Answer 2

It means, don't assume my insides match my outsides. It's kinda like, "Don't judge a book by its cover." Someone may be wearing pants, but that doesn't mean that they are in charge. Appearances are deceiving.

Answer 3

Hmm. Is this a circus clown pick-up line?

Answer 4

Perhaps they are referring to the expression "the one who wears the pants/trousers". If you say "she wears the trousers in their house" it means she is the boss. The person who said this might mean despite the fact that they are the boss, they are still approachable, nice and not bossy at all.