换了个人 - Chinese Idiom

换了个人

Literally means:

change into different man

Actually means:

(of a person) assume a new look

It means that a person's behavior is diametrically different from what people remembered as if he were a different person now. Usually used to describe a person whose appearance or behavior has changed dramatically with a sense of exaggeration.

一个人的行为举止与人们印象中的大不一样，就像变成另外一个人一样了。多用于指某人的外表或举止发生了很大的变化，有夸张的意味。