keep (one's) wig on

To remain calm and composed while waiting for something. Usually used as an imperative in the phrase "keep your wig on." If all those investors would just keep their wigs on instead of jumping ship at the first sign of danger, the company might have had a chance to recover from the poor reception of their latest hardware. A: "Bill? Bill? Hey, Bill! C'mon, what's the hold up?" B: "I'm coming, I'm coming. Sheesh, keep your wig on!"