David Cash

A person who is originally seen as a quiet, laid back guy who does what he pleases, but suddenly decides to change his style and attitude for unknown reasons.

Possibly a stoner.

Guy 1: "Did you hear that <insert name> joined that group of bros?"

Guy 2: "<insert name>?! No way! That's not like him."

Guy 1: "I know, man. A total David Cash."