We are shown that people may not always be quite what they appear to be.

Aliases:
don't judge a book by its cover

References:
https://www.merriam-webster.com/dictionary/looks%20can%20be%20deceiving/deceptive https://idioms.thefreedictionary.com/appearances+can+be+deceiving https://en.wikipedia.org/wiki/Don%27t_judge_a_book_by_its_cover