Pretty is as pretty does proverb
Used for men or boys: Handsome is as handsome does.
Just based on your attractive physical appearance, it is not enough to assess you as a kind person. (Usually said of girls or women)
A: Despite her lovely face, she tends to spread malicious gossip. B: Pretty is as pretty does, you know.
Mary is living proof that pretty is as pretty does. She looks gorgeous yet abrupt with anyone around her.
The proverb was first recorded by Chaucer in 'The Wife of Bath's Tale' (c. 1387)
Children or adults often say this phrase to get their friends to join in something, especially to jump into a swimming pool (pond, lake, etc.)
“Last one in is a rotten egg!” yelled Jane, jumping into the pool.