Preview Piggybacking

Basically this is when a work sells itself on including a preview for a much more anticipated work. This is often done with second string titles that would fizzle out on their own. This has become less prevalent (or at least less successful) with the rise of easier video sharing and video game demos on the Internet, but still there are some fandoms dedicated enough to shell out cash for a ticket to Movie You Might Have Ignored Completely if it means they get a chance to see just an ad for Everything You Ever Liked: The Movie.

This is also done on TV shows. You get a trailer (more often called a "sneak peek") packed somewhere in the commercials (although usually at the end) for an anticipated blockbuster.

The inverse is standard procedure, where an anticipated work includes a preview for a less-hyped title, in the hope that attention will rub off on it.

Film

 * Meet Joe Black, The Waterboy and The Siege were showing the teaser trailer for Star Wars Episode I: The Phantom Menace.
 * And to make sure you didn't leave the theater, Meet Joe Black showed it again after the credits.
 * Later, the second trailer was shown just before the Wing Commander film.
 * The final trailer got attached to the box office flop The Mod Squad.
 * One of the Pokémon movies had many cinemas deny refunds in case people just came to watch the Harry Potter trailer.
 * The Scooby Doo film attracted fans because of a preview for Chamber of Secrets.
 * Fellowship of the Ring was a weird version of this. It was already a hit when a trailer for The Two Towers was put into the film. So many people saw it again for the trailer, even though we were anticipating the previewed film because of the piggybacking film.
 * Same thing happened with Back to The Future Part II, as it had the trailer for Part III before the credits.
 * The 2008 remake of The Day the Earth Stood Still was advertised as being the only place to see the trailer for X-Men Origins: Wolverine.
 * Similarly, there were huge billboards in the UK advertising a three-part trailer during 24: Redemption.
 * Fans of Kevin Smith were known to have purchased tickets to Scary Movie 2 in order to see the exclusive Jay and Silent Bob Strike Back trailer.
 * The adaptation of Stephen King's 'Dreamcatcher was front-loaded with Final Flight of the Osiris, a short film that led directly into (and served as a teaser for) The Matrix Reloaded.
 * Bandslam, starring Vanessa Hudgens, was the launchpad for the first trailer of The Twilight Saga: New Moon.
 * Similarly, in Sweden, Kick Ass was actually advertised, in papers, with "Don't miss the Eclipse trailer!".
 * Summit later used Remember Me to launch the Eclipse trailer.
 * J.J. Abrams has been known do this for announcing new projects. The first trailer for Cloverfield was shown before Transformers before production even started. Same thing with Super 8 being shown before Iron Man 2 and within Portal 2.
 * The Jet Li film Hero was delayed for two years in the US so Harvey Weinstein could release the trailer before prints of Kill Bill.
 * Ten years before The Phantom Menace, Batman fanboys bought tickets for Tequila Sunrise just to see the teaser to Tim Burton's Batman.
 * Some films are even reissued solely because of this trope. Examples include: The Empire Strikes Back before Star Wars, Return of the Jedi before Star Wars and The Empire Strikes Back, Pulp Fiction before Reservoir Dogs and Pocahontas before The Lion King.
 * The movies of Adam Sandler have been doing this lately. Just Go with It had Zookeeper (with Sandler voicing a monkey) attached to it and that movie had Jack and Jill attached. Both times, the trailer didn't really fit with the movie.
 * The trailer for Machete was attached to prints of Predators due to Robert Rodriguez and Danny Trejo working on both films. Audiences were probably in for a shock when after seeing Trejo mow down Border Patrol and Hungarian bodyguards in the trailer,.
 * The trailer for Die Another Day was attached to prints of Austin Powers In Goldmember as the result of a settlement between MGM and New Line Cinema over using the name "Goldmember" (which MGM felt sounded too similar to Goldfinger).
 * The only place to see an early mini-trailer for The Avengers was after the credits of Captain America: The First Avenger.
 * An odd example with Sherlock Holmes a Game of Shadows and Mission Impossible: Ghost Protocol. While the first full theatrical trailer for The Dark Knight Rises was attached to Sherlock Holmes, it lost the opportunity to show the six-minute prologue to Mission Impossible, causing many a headache for execs at Warner Bros.
 * And only select prints got the trailer. Most prints of Sherlock Holmes had Rock of Ages and Jack the Giant Killer attached.

Literature

 * The Warrior Cats and Seeker Bears book often have preview pages for the next book, being written by the same author. In fact, one of the main selling points of the summer 2012 release Enter The Clans is that it contains a teaser for Survivors, the new (not really) Erin Hunter series, and the fifth Super Edition, Yellowfang's Secret.

Live Action TV

 * Warner Bros. promoted the exclusive "first look" of Poseidon during the 2006 Super Bowl and, well... it was pretty easy to tell from that ad that the movie wasn't going to be making the $160 million that it would need to break even.
 * South Park made fun of this in the episode "The New Terrance and Phillip Movie Trailer", where the boys had to sit through a showing of "Russell Crowe: Fightin' Round the World" in order to see the trailer. Hilarity Ensues.
 * Lost buried promos for upcoming episodes in commercial breaks for V-2009. This was inverted when the latter show ran a pop up ad during the former that blocked relevant onscreen content.
 * Pokémon Sunday has brief bits of news about the upcoming games.

Video Games

 * Zone of the Enders was at the time of its release widely known as the free game that came with the demo for Metal Gear Solid 2 Sons of Liberty. How much bought just the demo and ignored the game is hard to tell. But it got a Sequel, a spinoff, and two Animes, so evidently some people liked the game.
 * It didn't sell well enough for Konami to give a damn about localizing the sequel, though. No, it did come over here. But arguably in the worst way possible. (Which is a shame, since the fairly weak GBA game had a stellar localization by contrast.)
 * Similarly, the HD collection of the series includes a demo for Metal Gear Rising Revengeance. Lampshade Hanging or Mythology Gag? You decide.
 * Crackdown didn't have a demo for Halo 3 (since demos can just be downloaded from Xbox Live), but it had access to the multiplayer beta. Crackdown was expected to get loads of returns after the beta closed, but that was not the case. In fact, Microsoft reported that the Crackdown multiplayer got more play time than the beta (although the actual release of Halo 3 got even more, predictably). Combined with the critical acclaim the game received, Microsoft stated they want a sequel, which they got at E3 2009. It didn't have access to the Halo: Reach multiplayer beta (Halo 3: ODST fills in the spot this time).
 * Square Enix made a habit of this:
 * Tobal No. 1 had a Final Fantasy VII demo and movies of Final Fantasy Tactics, Bushido Blade, and Saga Frontier. It's highly likely that two thirds of the (subpar) sales were just for it, and even today Tobal is a heatedly sought collector's item for Final Fantasy fans, just for the demo that came with it.
 * Parasite Eve had a demo for Xenogears and movies for Bushido Blade II, Brave Fencer Musashi, and Final Fantasy VIII.
 * Brave Fencer Musashi had a Final Fantasy VIII demo. This is not dissimilar to the above Crackdown and Zone of the Enders examples, as Musashi has gained quite a reputation and cult following in the years following its release.
 * They've even done this with music releases. The soundtrack for Final Fantasy the Spirits Within includes a movie for Final Fantasy X.
 * Vagrant Story had a disc with demos for, among others, Threads of Fate.
 * In Europe, the Playstation port of Final Fantasy VI came bundled not with Final Fantasy V as in America (That came with Final Fantasy IV. Chrono Trigger was left unreleased. Again.), but with a demo of Final Fantasy X, which wouldn't even work on the console the piggybacked game was made for, though both discs were playable on a Play Station 2.
 * Spanish magazine Hobby Consolas said the demo and the FMV were the best thing about the game. Fans were not pleased. Then again, they made a lot of factual mistakes about the same...
 * Dragon Quest VIII included a demo of Final Fantasy XII in the US (neither series would need such a thing in Japan). This did help the game achieve gold sales in the US, probably a best for the series so far.
 * Unlimited Saga takes this Up to Eleven, with more work actually being put into the Final Fantasy X demo than the game itself. People vaguely remember some not very good RPG that came with A PLAYABLE DEMO FOR FFX!
 * A short demo for first-person shooter Area 51 was available in Mortal Kombat Deception.
 * The Play Station 2 version of Mega Man X Command Mission included the intro stage of Mega Man X8 as a demo.
 * The God of War Collection (GoW I and II remastered for the PlayStation 3) includes a voucher for the God of War III demo.
 * A few people preordered Mario Kart: Double Dash for the Sonic Heroes demo included on the preorder bonus disc (among other demos and videos, such as bonus items added to Fire Emblem 7).
 * In Famous came with access to the Uncharted 2 multiplayer beta.
 * They did it again: In Famous 2 came with access to the Uncharted 3 multiplayer beta. It's safe to say that Sucker Punch and Naughty Dog really like promoting each other.
 * Fighting Force was rereleased with a demo of Tomb Raider III.
 * Borderlands got a "Game of the Year" edition rerelease with all currently available Downloadable Content and a code that allows access to the Duke Nukem Forever First Access Club, so they could be among the first to play the demo.
 * Much like Halo 3 up above, the Epic Edition release of Bulletstorm on the Xbox 360 shipped with a voucher for the Gears of War 3 beta.
 * Resident Evil-related examples:
 * Resident Evil: Director's Cut included a demo for Resident Evil 2.
 * Certain copies of Dino Crisis came with a demo for Resident Evil 3 Nemesis and vice-versa.
 * The Japanese Dreamcast port Resident Evil 2 came with a demo for Resident Evil Code Veronica.
 * The Play Station 2 version of Resident Evil Code Veronica X came with a demo for Devil May Cry.
 * Sonic Mega Collection had the trailer for Sonic Heroes on it.

Western Animation

 * On the day of May 28, 2011, many bronies went to their TV sets and watched Garfield: The Movie just to see the Equestria Girls commercial.

Cross-medium

 * The District 9 Blu-Ray contains the God of War III demo.
 * The Steam version of Portal 2 contains an interactive sneak peek at Super 8.
 * The Star Wars Trilogy DVD set contained a demo of the X Box version of Star Wars Battlefront.
 * A Spongebob BC DVD had a demo for the PC version of Battle For Bikini Bottom on it