A shout out is something subtle (a name, line of dialogue, or prop) in a show that refers to fans or family members of the cast or crew, or to another source of inspiration. By nature, these can be obscure for casual fans.
You can even talk about them in English class if only you call them "allusions". However, remember that many tropes, symbols, and such are older than they look and can, often, arise in parallel. So despite (or because of) the ubiquitous nature of some creative properties that doesn't mean that anything that seems somewhat similar is referencing said work.
Reference Overdosed is when a series is loaded with these.
Giving references to other works can predate to older times but became increasingly common in medieval times. In modern times, almost every larger film, video game and so on intentionally references some other work, making the phenomenon nearly omnipresent.
See also Homage, Stock Shout Outs, Opening Shout-Out, Shout Out Theme Naming. Literary Allusion Title is a subtrope. Easily confused with a Mythology Gag and Continuity Nod, and may overlap with Actor Allusion. Contrast Take That, which is a negative-spirited Shout Out.
See Stock Shout Outs for a list of Shout Outs and other references common enough to earn their own page.
Remember, a Shout Out is intentional. If a character just happened to use a similar turn of phrase to another work, that's just a coincidence.
Be it novel, video game, comic or TV show, anything related to Star Wars will do this without shame. We can only assume the makers of Pepto-Bismol must be filthy rich in this universe, what with everyone having a bad feeling about this and that...
When one registers for online content on the St. Louis Post-Dispatch website, one of the password recovery questions asks for the airspeed of an unladen swallow.
Advertising
A Filipino snack ad best described, as one comment put it, as "SACRILEGE TO LUCKY STAR." In terms of character designs, Sailor Moon wasn't spared either.
There's a Honda advertisement that uses the opening to the Waldstein Sonata by Beethoven.
Card Games
Steve Jackson Game's Hacker includes a can of Jolt cola◊ on the box picture.
The Collectible Card GameMagic: The Gathering likes to slip Shout Outs and in-jokes into the titles and art of its cards. Probably the most high-profile (that references something outside of M:tG itself anyway) is Nevinyrral's Disk. "Nevinyrral" is "Larry Niven" spelled backwards. Niven wrote a series of stories about magic as an exhaustible resource, the nature of which was proven in the story "The Magic Goes Away" by a wizard who enchanted a spinning disk in such a manner that it used up all the mana in its vicinity, exploding violently in the process.)
The Star Wars Customizable Card Game is made of this trope: Smuggler's Blues obviously, but also Mostly Armless and Bionic Hand "We can make him better, stronger, faster."
Yu-Gi-Oh! Card Game is absolutely loaded with Shout Outs to Konami games, mostly notably the Gradius archetype: so far, a card exists for the original ship, an upgraded version of same, the second player ship, the ships from Gradius Gaiden, most of the various ship bosses (complete with support card Boss Rush), the game's power-ups, at least three of the other various bosses, and at least five of the game's enemies. Plus, they synergize pretty well with the cards based on the protagonist ships in Xexex and Thunder Cross. And let's not even get into the set of Union Monsters based on Aitsu, Koitsu, Soitsu, and Doitsu...
Seriously, DO NOT play the TV Tropes Drinking Game if you plan on including all the ShoutOuts in this thing. It'll be very, very bad for your health.
How bad is it? The summary (Two Dalek Empires fight for the future of the Dalek race) is a Shout Out to Remembrance Of The Daleks and it just goes downhill from there.
In The Lie I've Lived, a throwaway line has Harry saying, "Yeah, just call me 'Ambassador Potter', expert at foreign diplomacy and purveyor of international goodwill." This refers to one of author's other works Bungle in the Jungle.
Lord of the Land of Fire is prone to lacing the plots of his stories with references to things like World War II or The Book of Revelation, among other things.
Hogfather: The noble music which plays when Bilious is being sobered up is of course Men of Harlech, but is also known to some university students as The Alcoholics' Anthem.
For the last several years, Rey Mysterio Jr has appeared at Wrestlemania wearing a costume clearly inspired by a fictional character. This used to be pretty much just superheroes, but last year, he was dressed as The Joker... and then this year, he was one of the Na'vi from Avatar
He was recently dressed in an homage to Iron Man (probably in commemoration of the movie sequel's release in theaters), and his WrestleMania debut (WrestleMania XIX, in a Cruiserweight Title match against defending champion Matt Hardy) was as The Flash...which happens to be his most frequent special-occasion costume.
A possibly unintentional pair of shout-outs for the WWE when the theme songs to RAW and Smack Down were changed to "Burn It to the Ground" by Nickelback and "Let It Roll" by Divide The Day, respectively; both songs (whether intentionally or not) sound very similar to the original debut themes for both shows (RAW's untitled original theme and Smack Down's original theme, "Everybody On the Ground", respectively)
Prior to making his entrance, CM Punk will stop at the stage and shout "It's clobberin' time!" prior to his matches.
Radio
Garrison Keilor and Ira Glass have a fake feud going on, whereby they slip little insults to one another into their respective radio shows or public appearances. In Keilor's case, these often take the shape of mentions of Glass in his Prairie Home Companion sketches, impressions of Glass done by his actors, or pastiches of Glass' broadcasting style.
The ersatz Keilor/Glass feud is itself a shout-out to Jack Benny and Fred Allen, two giants of the Golden Age of Radio, who first hit upon this idea as a running (and recognised) prank on the audience.
Keilor also mercilessly lampoons other NPR figures in sketches, most notably news correspondents, who show up as voice impressions in PHC news sketches. Sometimes these pseudo-cameos are identified by name; often they are either un-named or given a ficitonal name, making the shout-out an inside joke among NPR staff and habitual listeners.
Toys
In G.I. Joe, the redheaded Shana O'Hara was born in the South (specifically, Atlanta, Georgia). She is, indeed, a fierce and attractive Southern belle. Her codename? Scarlett.
Real Life
A lot of taxonomic names end up being Shout Outs to things. Often it's to the scientist who discovered it or to the location it was discovered, but there are some more unusual ones:
A spongelike fungus is named spongiforma squarepantsii.
Interesting story behind Utahraptor spielbergi — scientists felt the raptors in Jurassic Park were too big, so when they did find ones at that size they named the species after the movie director.
Velociraptors were about four feet tall. The filmmakers didn't think that would be scary enough and beefed 'em up.
Sadly, though, Spielberg's lawyers rejected, so it was renamed Utahraptor ostrommaysorum, after John Ostrom, who discovered Deinonychus and established the dromaeosaurs as a family in the progress, and Chris Mays of Dinamation, which funded the expedition that discovered Utahraptor.
There are several flower varieties called Sailor Moon. Surprisingly, Naoko Takeuchi makes one of them as part of an artbook drawing, since she loves when fans homage her works, and compliments it back as she can.
Strigiphilus garylarsoni, a kind of chewing louse, after the creator of The Far Side and his frequently insect-related humour.
The "Ogg" multimedia format is not a reference to Nanny Ogg; however once the coincidence was pointed out, the makers named their audio format after Vorbis from Small Gods.
The trapdoor spider Myrmekiaphila neilyoungi, and inevitably, Aptostichus stephencolberti.
The scientific name for the dinosaur Masiakasaurus is Masiakasaurus knopfleri — the expedition crews were said to be listening to a lot of Dire Straits at the time. Mark Knopfler himself once made an amusing self-effacing comment about how appropriate it was to have a dinosaur named after him.
For a better reference, this disorder would leave him looking like a Raw Shock.
In addition, one of the macrocycle inhibitors of the gene sonic hedgehog continues the reference. It is named Robotnikin.
Likewise, a retinal protein was named Pikachurin, due to its relation with electrical signals.
Celestial bodies are also often named for real or fictitious people, in a tradition dating back to antiquity when planets and constellations were named for the gods.
A scientist named a rock in the Main Asteroid Belt 18610 Arthurdent". Later, another asteroid was dedicated to the author: 25924 Douglasadams
The naming of 25924 Douglasadams is itself a heartwarmer. The provisional name for it was 2001DA42. *
The year in which Douglas Adams died, his initials, and the Ultimate Answer to Life, the Universe, and Everything, in that order.
The only comments that could be given were along the lines of "it was sort of made for him, wasn't it?"
The asteroids 12796 Kamenrider and 12408 Fujioka, named for the Kamen Rider franchise and its original star, Hiroshi Fujioka.
A fantastic bonus for computer programmers: the number 46610, written in hexadecimal, is B612.
Asteroid 99942 Apophis. Even funnier, there is a small chance that the asteroid may hit Earth in 2036, so Apophis is our real-life enemy. (To clarify: the name Apophis comes from Egyptian Mythology, but the asteroid's discoverers are said to be fans of Stargate SG-1.)
There's even one named after the fictitious Czech genius Jára Cimrman.
Let's just say that the name of every other asteroid is a reference to something-or-other (since it's the discoverer who proposes the name, and there are few restrictions on the name choice.)
White dwarf BPM 37093 in the sky with a crystallized carbon core (read: diamond). Informally named: Lucy.
The dwarf planet now known as "Eris" was nicknamed "Xena" for 2 years while a final name and designation were decided. Its moon was officially named "Dysnomia" (Lawlessness) as a shoutout to actress Lucy Lawless.
Tanz Metal band Rammstein had a minor planet named after them.
All of the elements after plutonium, once they are actually synthesized, are named either for a famous scientist (einsteinium, bohrium, mendelevium, nobelium, rutherfordium) or an important location, usually the element's "place of birth" (berkelium, californium, americium, darmstadtium). An abandoned mine at Ytterby, in the Stockholm archipelago, has four elements named for it: erbium, terbium, ytterbium and yttrium.
Google's Wave service was named such because that's what communications were called in Firefly. The crash message is even Wash's infamous line "Curse your sudden but inevitable betrayal!"
Programmers love to do this. Examples include:
Soylent, a project to merge all contact info (e-mail addresses, IM screennames, etc.) for a person into a single account in GNOME (Linux-and-its-ilk desktop).
Along with Plan 9 From User Space, a port of the main Plan 9 programs to UNIX-like systems. (and yes, userspace actually means something in context)
The TIFF standard specifies "An arbitrary but carefully chosen number (42)."
The ADA programming language, named after Ada Lovelace, who's often credited to be the world's first programmer. ADA was created under contract from the United States Department of Defense, which gave the ADA reference manual the number MIL-STD-1815. 1815 was Ada Lovelace's year of birth.
The Python programming language was named after Monty Python.
The term "Spam" for junk e-mail was named after the Monty Python sketch of the same name.
Other people backronymed it to Stupid Pointless and Annoying Message.
While not a shout out to pop culture most of the time the codenames for AMD, Intel, and Microsoft products tend to be named after places they either do development in, take vacations to, or just because.
AMD's first in-house designed x86 compatible processor was called K5. Their next generation, K6, was when they said the K meant Kryptonite.
Upcoming iterations of Nvidia's Tegra system-on-a-chip series are codenamed Kal-El, Wayne, Logan, and Stark.
The Raspberry Pi (an educational- / hobbyist-market computing device with an ARM CPU, capable of running Acorn RISC OS) is available in "Model A" and "Model B" versions; this will sound familiar to anyone who remembers the BBC Micro. (It's no coincidence that this device was co-developed by David Braben, of Elite fame.)
Originally Colbert was competing for the naming of a space capsule, the name in second place was Serenity.
We swear someone literally shouted out "I see you,Russia!" before that pair's free skate...
Or it could more likely be a reference to the statement by Sarah PalinTina Fey that you could see Russia from Alaska, and that in itself gave her international relation experience.
Iron Maiden's drummer Nicko McBrain owns a restaurant, Rock N' Roll Ribs. The menu is filled with references to his band (such as "Appetite of THE BEAST", and the temperatures of sauce: Mild, Medium, Hot, Die with your Boots On, or Heaven Can't Wait).
How could we forget Lucy, the fossilized Australopithecus named after the Beatles song "Lucy in the Sky with Diamonds".
