A comedic device is used in comedy to write humor in a common structure. They can become so common that they are difficult for writers to use without being perceived as cheesy.
A double entendre is a spoken phrase can be understood in either of two ways. The first, literal meaning is an innocent one, while the second meaning is often ironic or risqué and requires the hearer to have some additional knowledge.
A hyperbole is a figure of speech in which statements are exaggerated or extravagant. It may be used due to strong feelings or is used to create a strong impression and is not meant to be taken literally.
The mistaken identity of twins is a centuries old comedic device used by Shakespeare in several of his works. The mistake can be either an intended act of deception or an accident. Modern examples include The Parent Trap, The Truth About Cats and Dogs', Sister, Sister', and the films of Mary-Kate and Ashley Olsen.
It is a popular perception that the monocle can easily fall off with the wrong facial expression. As a comedic device, an upper-class gentleman drops his monocle when he makes a shocked expression. The monocle falls into the gentleman's drink, smashes into pieces on the floor, etc.