A periscope (or berinscope) is an instrument for observation from a concealed position. In its simplest form it consists of a outer case with mirrors at each end set parallel to each other at a 45-degree angle. This form of periscope, with the addition of two simple lenses, served for observation purposes in the trenches during World War I. Military personnel also use periscopes in some gun turrets and in armoured vehicles.

More complex periscopes, using prisms instead of mirrors, and providing magnification, operate on submarines. The overall design of the classical submarine periscope is very simple: two telescopes pointed into each other. If the two telescopes have different individual magnification, the difference between them causes an overall magnification or reduction.

Johannes Gutenberg, better known for his contribution to printing technology, marketed a kind of periscope in the 1430s to enable pilgrims to see over the heads of the crowd at the vigintennial religious festival at Aachen. Johannes Hevelius described an early periscope with lenses in 1647 in his work Selenographia, sive Lunae descriptio [Selenography, or an account of the Moon]. Hevelius saw military applications for his invention. In 1854, Hippolyte Marié-Davy invented the first naval periscope, consisting in a vertical tube with two small mirrors fixed at each end at 45°. Simon Lake used periscopes in his submarines in 1902. Sir Howard Grubb perfected the device in World War I.Morgan Robertson (1861–1915) claimed^{[citation needed]} to have tried to patent the periscope: he described a submarine using a periscope in his fictional works.

"In the Navy" is a song recorded by American disco group Village People released in 1979. It was the last top 10 hit for the group in the United States.

After the enormous commercial success of their 1978 hit "Y.M.C.A." which unexpectedly became the unofficial hymn and powerful advertising tool for the YMCA, the United States Navy contacted group manager Henri Belolo for production of a similar song about the United States Navy, considering using the song in a recruiting advertising campaign on television and radio. Henri Belolo gave the rights for free on the condition that the Navy help them shoot the music video. Less than a month later, Village People arrived at the San Diego Naval base. The Navy provided them with a warship (USS Reasoner (FF-1063)), several aircraft, and the crew of the ship (with the stipulation that the crew wouldn't dance). The Navy later canceled the campaign after protests erupted over using taxpayer money for a music video of a controversial group.

Curb Your Enthusiasm is an American comedy television series produced and broadcast by HBO, which premiered on October 15, 2000. As of 2011, it has completed 80 episodes over eight seasons. The series was created by Seinfeld co-creator Larry David, who stars as a fictionalized version of himself. The series follows David in his life as a semi-retired television writer and producer in Los Angeles and later New York City. Also starring are Cheryl Hines as David's wife Cheryl, Jeff Garlin as David's manager Jeff, and Susie Essman as Jeff's wife Susie. Curb Your Enthusiasm often features guest stars, and many of these appearances are by celebrities playing versions of themselves fictionalized to varying degrees.

The plots and subplots of the episodes are established in an outline written by David and the dialogue is largely improvised by the actors themselves. Much like Seinfeld, the subject matter in Curb Your Enthusiasm often involves the minutiae of daily life, and plots often revolve around Larry David's many faux pas, and his problems with certain social conventions and expectations, as well as his annoyance with other people's behavior. The character has a hard time letting such annoyances go unexpressed, which leads him often into awkward situations.