In theater, an understudy is a performer who learns the lines and blocking/choreography of a regular actor or actress in a play. Should the regular actor or actress be unable to appear on stage because of illness or emergencies, the understudy takes over the part. Usually, when the understudy takes over, the theater manager will make the announcement prior to the start of the performance.

In the opera world, the term cover or covering is used.

More recently, the term "understudy" has generally only been applied to performers who will cover a part, but still regularly perform in another role within the show; usually a minor, extra role.

Performers who are only committed to covering a part and do not regularly appear in the show are often referred to as standbys. Standbys are normally required to sign-in and remain at the theater the same as other cast members, although sometimes they may call in, until they are released by the Production Stage Manager. If there is no doubt about the health of the actor being "covered," or there are no hazardous stunts to be performed, a standby may be released at the first intermission if not before. At times, standbys are required to stay within a certain area around the theater (10 blocks in New York City is a common standard). The standby must also have a cell phone so that at any time they can be called to the theater.

Joseph-Michel Montgolfier (26 August 1740 – 26 June 1810) and Jacques-Étienne Montgolfier (6 January 1745 – 2 August 1799) were the inventors of the montgolfière-style hot air balloon, globe aérostatique. The brothers succeeded in launching the first manned ascent, carrying Étienne into the sky. Later, in December 1783, in recognition of their achievement, their father Pierre was elevated to the nobility and the hereditary appellation of de Montgolfier by King Louis XVI of France.

The brothers were born into a family of paper manufacturers in Annonay, in Ardèche, France. Their parents were Pierre Montgolfier (1700–1793) and his wife, Anne Duret (1701–1760), who had sixteen children. Pierre established his eldest son, Raymond Montgolfier, later Raymond de Montgolfier (1730–1772), as his successor.

Joseph, the 12th child, possessed a typical inventor's temperament—a maverick and dreamer, and impractical in terms of business and personal affairs. Étienne had a much more even and businesslike temperament. As the 15th child, and particularly troublesome to his elder siblings, he was sent to Paris to train as an architect. However, after the sudden and unexpected death of Raymond in 1772, he was recalled to Annonay to run the family business. In the subsequent 10 years, Étienne applied his talent for technical innovation to the family business; paper making was a high-tech industry in the 18th century. He succeeded in incorporating the latest Dutch innovations of the day into the family mills. His work led to recognition by the government of France as well as the awarding of a government grant to establish the Montgolfier factory as a model for other French paper makers.

Theresa Rebeck (born c. 1958) is an American playwright, television writer and novelist. Her work has appeared on the Broadway and Off-Broadway stage, in film, and on television. Among her awards are the Mystery Writers of America’s Edgar Award.

Rebeck was born in Kenwood, Ohio, and graduated from Cincinnati's Ursuline Academy in 1976. She earned her undergraduate degree at the University of Notre Dame in 1980, and followed that with three degrees from Brandeis University: an MA in 1983, a M.F.A. in Playwriting in 1986, and a Ph.D. in Victorian era melodrama, awarded in 1989.

Past New York productions of her work include Mauritius on Broadway at the Biltmore Theatre in a Manhattan Theater Club Production; The Scene, The Water’s Edge, Loose Knit, The Family of Mann and Spike Heels at Second Stage Theatre; Bad Dates and The Butterfly Collection at Playwrights Horizons; and View of the Dome at New York Theatre Workshop. Omnium Gatherum (co-written, finalist for the Pulitzer Prize for Drama in 2003) was featured at the Humana Festival, and had a commercial run at the Variety Arts Theatre in 2003. Her play The Understudy, premiered at the Williamstown Theatre Festival in the summer of 2008, with a cast including Reg Rogers, Bradley Cooper and Kristen Johnson, and ran in New York at the Roundabout Theatre from October 2009 - January 2010, featuring Julie White, Justin Kirk, and Mark-Paul Gosselaar in the cast. Rebeck is also writing the book for the new musical Ever After, based on the Drew Barrymore movie of the same name. That show was expected to start pre-Broadway tryouts in San Francisco in April 2009, but has been indefinitely postponed. Her play, Mauritius, ran at the Pasadena Playhouse in California from March 27 through April 26, 2009.

Melissa Joan Catherine Hart (born April 18, 1976) is an American actress, writer, television director, television producer, singer and businesswoman. Hart is perhaps best known for her title roles in the television series Clarissa Explains It All (1991–1994), the live action version of Sabrina, the Teenage Witch (1996–2003), and Melissa & Joey (2010–present).

Hart's career has mixed movie work with television, including appearances in the popular TV shows Law & Order: Special Victims Unit and That '70s Show. Hart has been married to musician Mark Wilkerson since July 19, 2003 (married in Firenze); together, they have two children and in April 2012 announced they are expecting their third child.

Hart was born April 18, 1976 in Smithtown, New York, on Long Island, the first child of Paula, a producer and talent manager, and William Hart, a carpenter, shellfish purveyor, clam hatchery worker, and entrepreneur. She grew up in Sayville, New York. Her parents had four other children after Melissa: Trisha, Elizabeth, Brian, and Emily. Her parents were divorced in the early 1990s, and she moved with her mother and siblings to New York City. In 1994 her mother married television executive Leslie Gilliams, and her father also remarried (Lisa Hart).

Kirsten Wyatt (born c. 1975) is an American Broadway actress portraying Frenchy in the new Broadway revival of Grease.

Wyatt grew up in Clarksburg, West Virginia. Since completing her training at the University of Cincinnati College-Conservatory of Music in 1997, Wyatt has appeared in a number of Broadway productions. Her Broadway premiere was as the understudy for Kristin Chenoweth (Sally Brown) and Ilana Levine (Lucy van Pelt) in the 1999 revival of You're a Good Man, Charlie Brown. Other notable Broadway roles include Little Becky Two Shoes in Urinetown and Allison and Anna in High Fidelity. She has recently been confirmed to be appearing in the ensemble of the upcoming musical adaptation of Elf on Broadway.

Wyatt has also been a member of the national touring casts of Urinetown and The Boy Friend (directed by Julie Andrews). Her regional credits include Peter in Peter Pan and Eponine in Les Misérables. She also performed in The Joe Iconis Rock 'n Roll Jamboree.

She is married to musician Sean Nowell.