[Nancy Snyder as Joan in "Knock Knock".]

[Daniel Seltzer as Cohn and Nancy Snyder as Joan in "Knock Knock".]

[Nancy Snyder as Joan, Neil Flanagan as Abe and Daniel Seltzer as Cohn in "Knock Knock".]

["Knock Knock" theater still.]

["Knock Knock" theater still.]

["Knock Knock" theater still.]

[John Heffernan as Abe in "Knock Knock".]

["Knock Knock" theater still.]

[Daniel Seltzer as Cohn in "Knock Knock".]

[Jules Feiffer and the cast of "Knock Knock".]

[Neil Flanagan as Abe in "Knock Knock".]

["Knock Knock" theater still.]

[Curtain call for "Knock Knock".]

[Neil Flanagan as Abe in "Knock Knock".]

["Knock Knock" theater still.]

[Jules Feiffer and the cast of "Knock Knock".]

[Charles Durning as Cohn in "Knock Knock".]

[Neil Flanagan as Abe and Daniel Seltzer as Cohn in "Knock Knock".]

[Daniel Seltzer as Cohn in "Knock Knock".]

[Leonard Frey in "Knock Knock".]