Finally, a hard hitting question into which I can sink my teeth. I called Rachael Stanley at the Costume Designer’s Guild and posed the query to her. She laughed and said, “Generally, the costume department provides the actor with everything.”

While there might be some leeway with an actor wearing his own underwear, particularly if it won’t show up on screen, actresses almost always have to wear underwear supplied by the costume department. Explained Stanley, “You want to make sure that the actress’ bra doesn’t show through her top and that she doesn’t have any underwear lines that are visible.”

Even if an actor or actress’ underwear isn’t visible, it can play a part in how the thespian’s clothes hang. “Sometimes, if an actor is wearing boxers, they’ll bunch up and change the look of his outfit,” Stanley stated. “In that case, you offer the actor briefs.”

Just when I thought I couldn’t possibly learn anything more about the presence of underwear on a film set, Stanley mentioned that in period pieces, it’s up to the costume department to create time-sensitive lingerie. In those cases, it’s imperative that the actors and actresses wear the underwear supplied by the production, lest the viewer be taken out of the moment by an errant glimpse of a WonderBra.