Dual role
A dual role refers to one actor playing two roles in a single production. Dual roles may be deliberately written into a script, or may instead be a choice made during production, often due to a low budget. In film and television, dual roles are often used for comic effect, or to depict identical twins or relatives. In a theatrical production where more than one actor plays multiple characters, it is sometimes referred to as an "Ironman" cast.
Theatre
In theatre, the use of multiple roles may be budget-related, may be intended to give an accomplished actor more stage time or a greater challenge, or may be of thematic significance to the story. The combination of factors leading to such a decision may often remain unknown. For example, debate exists over the significance of William Shakespeare's use of dual roles, with a notable example being whether the characters of Cordelia and the Fool in King Lear were intended to be one and the same, or whether the mysterious Third Murderer in Macbeth is actually Macbeth himself. In the musical Hamilton, four actors/actresses are cast in dual roles, each a major supporting character, with a change of roles between the first and second acts. The actors who play John Laurens/Philip Hamilton, Marquis de Lafayette/Thomas Jefferson, and Hercules Mulligan/James Madison wear identical white costumes in the opening song, "Alexander Hamilton", and were given lines with intentional double meanings that would fit either of their dual roles.In the original West End production of J. K. Rowling’s Harry Potter and the Cursed Child Parts One and Two many roles are doubled including Uncle Vernon/Severus Snape/Lord Voldemort, Aunt Petunia/Madame Hooch/Delores Umbridge, Amos Diggory/Albus Dumbledore, Trolley Witch/Minerva McGonagall, Cedric Diggory/James Potter Jr./James Potter Sr., Dudley Dursley/Karl Jenkins/Viktor Krum, and Rose Granger-Weasley/Young Hermione.
File:The Jury of Fate.jpg|thumb|200px|right|Mabel Taliaferro plays twin brother and sister in The Jury of Fate, where the sister assumes the brother's place after he is killed
Film
In a reverse situation, one character may be portrayed by multiple actors on rare occasions. Heath Ledger was cast as the lead in Terry Gilliam's The Imaginarium of Doctor Parnassus. However, he died before completing production, albeit with most of his main scenes completed. So Gilliam cast Johnny Depp, Colin Farrell, and Jude Law as "transformations of the main character in magical realms" to finish production.Tamil actors, Kamal Haasan came in multiple roles in more than fifteen films and also in 2008 film Dasavathaaram. He broke the record by doing 10 different characters in single film and Ajith Kumar have done dual roles in seven films. Starting in the 1970s, he had a living double in a Bollywood film became "almost a genre in itself," according to filmmaker Govind Nihalani.