adorn (oneself) with borrowed plumes

To make a showy display of something that is not truly one's own. I know you lied to me earlier about your involvement in this fair, so quit adorning yourself with borrowed plumes and tell me what you actually contributed. Please, I'm the one who did all the work coordinating the speakers. If Vanessa gets up to the mic and takes credit, she's just adorning herself with borrowed plumes. The hosts always adorn themselves with borrowed plumes, when it’s really the event planner who makes sure these events go off smoothly.