Most Hollywood movies go by a different name—also known as a working title—until the film is released in theaters. These cinematic pseudonyms can be used to hide a film’s production from rampant fans or to keep costs low. Here are 14 working titles for popular Hollywood movies.

1. Working Title: "Blue Harvest"

Actual Title: Return of the Jedi

By the time filming on Return of the Jedi started in 1982, Star Wars was a gigantic pop culture phenomenon. Lucasfilm decided to use a working title to mask the film’s production from fans and film journalists. “Blue Harvest” was used throughout the film’s production in the United States.

“Blue Harvest” was allegedly a horror film with the tagline “Horror Beyond Imagination.” It was used on almost every facet of the then-titled Revenge of the Jedi, including the crew's t-shirts, shipping crates, and invoices. The title Revenge of the Jedi was later changed to Return of the Jedi when George Lucas realized that a Jedi has no concept for the evils of revenge.

Another reason why “Blue Harvest” was used for the film’s working title was to keep production costs low: Apparently, locations and services had increased their prices when Lucasfilm was filming The Empire Strikes Back a few years before.

2. Working Title: "Planet Ice"

Actual Title: Titanic

Before the epic film Titanic was announced, director James Cameron began to shoot footage of icebergs off the coast of Nova Scotia under the guise he was making a film called “Planet Ice.” The reasoning behind the working title was to throw off any rival movie studio from making a movie based on Titanic before Cameron’s movie was in theaters.

3. Working Title: "Rory’s First Kiss"

Actual Title: The Dark Knight

When he was filming The Dark Knight in Chicago in 2007, director Christopher Nolan attempted to hide the true identity of the movie using the working title “Rory’s First Kiss." But the fake title wasn't enough to fool Batfans: When a casting call went out for "real police officers, sheriffs, county guards and bagpipers to work in non-speaking roles in August," a film journalist sniffed out the subterfuge after a quick look on IMDB.com, which identified Nolan as the director of “Rory’s First Kiss,” which also starred Christian Bale and Heath Ledger. It was easy to see that Nolan was working on the sequel to the widely popular Batman Begins.

Christopher Nolan used the working title “The Intimidation Game” for Batman Begins and also used the working title “Magnus Rex” for The Dark Knight Rises. For Nolan’s 2010 film Inception, the British director used the working title “Oliver’s Arrow.”

4. Working Title: "Incident on 57th Street"

Actual Title: Harry Potter and the Chamber of Secrets

To avoid attention from Harry Potter fans, the filmmakers behind Harry Potter and the Chamber of Secrets used the strange working title “Incident on 57th Street” throughout the film’s London shoot. Their inspiration? A Bruce Springsteen song of the same name.

5. Working Title: "How the Solar System Was Won"

Actual Title: 2001: A Space Odyssey

Arguably the greatest film ever made, director Stanley Kubrick and screenwriter Arthur C. Clarke secretly referred to their 1968 science fiction collaboration as “How the Solar System Was Won,” a reference to the 1962 Western from MGM titled How the West Was Won. When Warner Bros officially announced the sci-fi project in 1965, the press release called the film Journey Beyond the Stars.

Kubrick and Clarke eventually decided on the title 2001: A Space Odyssey 11 months into the film’s production. Other titles the pair considered were Universe, Tunnel to the Stars, and Planetfall.

6. Working Title: "Star Beast"

Actual Title: Alien

Screenwriters Dan O’Bannon and Ronald Shusett envisioned a new film that would be a science fiction and horror genre hybrid. Before settling on the title Alien, the pair’s screenplay was titled “Star Beast,” which was named after the terrifying Xenomorph alien in the movie. O’Bannon decided to change the title to simply Alien when he realized how many times the word was used in the screenplay.

7. Working Title: "The Seven Deadly Sins"

Actual Title: Se7en

In 1995, director David Fincher made a thriller called Se7en starring Brad Pitt, Morgan Freeman, and Gwyneth Paltrow. The film was originally titled “The Seven Deadly Sins” because the film featured a serial killer who used the capital vices as a way to murder his victims. The filmmakers changed the name of the film to build mystery and awareness of the movie before it opened in theaters.

8. Working Title: "Paradox"

Actual Title: Back To The Future Part II

“Paradox” was the title of the original pitch for the Back To The Future sequels. Originally, the film was conceived as one movie, but when the film’s budget grew too expensive, the film was split into two separate sequel films. Director Robert Zemeckis continued to use the working title as a way to lessen fan attention while shooting the films simultaneously.

9. Working Title: "Black Mask"

Actual Title: Pulp Fiction

When Quentin Tarantino and Roger Avery were working on the screenplay for Pulp Fiction, they originally titled the film “Black Mask,” as a way to pay homage to the hardboiled crime fiction magazine that popularized the pulp fiction genre in the 1930s and '40s. Later, the pair changed the name to emphasize the genre rather than a particular magazine.

10. Working Title: "Everybody Comes To Rick’s"

Actual Title: Casablanca

The film Casablanca was based on a then-unproduced stage play called “Everybody Comes To Rick’s.” While the authors of the stage play, Murray Burnett and Joan Alison, couldn’t find funding to produce the play on Broadway, Warner Bros bought the film rights for $20,000 in 1942. The title was changed to Casablanca as a way to imitate the 1938 smash-hit film Algiers.

11. Working Title: "Group Hug"

Actual Title: The Avengers

Marvel has special codenames or working titles for all of their films (the codename of Captain America: The First Avenger, for example, was “Frostbite”—because Captain America was encased in ice at the end of the film). For The Avengers, Joss Whedon chose the working title “Group Hug” to throw off eager fans. Tom Hiddleston told Elle magazine that the working title was fitting. “The Avengers was 'Group Hug,'" he said. "It felt very much like a group hug on set."

12. Working Title: "A Boy’s Life"

Actual Title: E.T. The Extra-Terrestrial

During the production of E.T., director Steven Spielberg used the working title “A Boy’s Life” in order to keep the film’s premise a secret—he didn’t want a competing film to beat him to the market. Actors had to be supervised when reading the script and everyone on set had to wear security ID cards to make sure the film shoot was secure.

13. Working Title: "Corporate Headquarters"

Actual Title: Star Trek

J.J. Abrams has a penchant for secrecy and mystery. During the production of the first Star Trek reboot, he used the working title “Corporate Headquarters” to throw off the scent of any snooping film journalists or fans. Security during production was extremely tight; each actor was under supervision while reading the film’s script or rehearsing scenes. But when a suspicious casting call asking for actors who had a “Vulcan-type eyebrow shape” emerged, reporters and fans soon found out that J.J. Abrams' new film was, in fact, Star Trek.

14. Working Title: "Changing Seasons"

Actual Title: Lord of the Rings: The Fellowship of the Ring

In 1998, it was no secret that Peter Jackson was adapting J.R.R. Tolkien’s sprawling epic of Middle Earth with the Lord of the Rings film trilogy. Jackson and his production team in New Zealand spent two long years making three movies simultaneously for the first film’s Christmas 2001 release date. When Fellowship of the Ring arrived at movie theaters around the world, the film canisters had the title “Changing Seasons” attached to them, so hardcore Tolkien fans would be fooled into thinking it was a different movie.

For the subsequent films—Two Towers and Return of the King—Peter Jackson used the titles “Grand Tour” and “Til Death, For Glory” respectively.