This is a withering put-down aimed at an actor whose performance is wooden, stilted or simply unconvincing. The paper bag is chosen because escaping one is about as easy as a task can get, so to say someone couldn’t manage even that is to say they are hopeless at their craft. It is almost always said of professionals who are being paid to perform and are judged to have failed badly, and it carries a note of ridicule rather than gentle criticism.
What’s the origin of the phrase ‘couldn’t act his way out of a paper bag’?
The phrase is a direct adaptation of an older insult built on the same image but a different verb. Dictionary.com traces the underlying template to the boxing world, where around 1910 it was used as a slur against a fighter judged too weak or too cowardly to be any good, the idea being that he lacked even the basic competence to punch his way clear of a flimsy paper bag. Wordhistories.net, drawing on OED research, records an early newspaper example of the fighting version, jeering that a man “could not fight your way out of a paper bag.”
Green’s Dictionary of Slang lists the construction as an established slang formula, headed in its own entry as “couldn’t fight their way out of a paper bag,” and notes that the verb slot is flexible rather than fixed, with citations recording the same frame used of other targets, such as “Silvers couldn’t fight his way out of a paper bag.” That flexibility is how the acting version came about. Once the insult had detached itself from boxing and become a general template for incompetence, “fight” could be swapped for whatever skill was actually in question. Applied to the stage or screen, “act” slots naturally into the same frame, turning a slur about physical toughness into one about dramatic talent while keeping the same absurd yardstick of failure. The paper bag stays constant throughout as the measure of a task so trivial that failing it proves total uselessness, whatever the field.