In 1989, it seemed like the Indiana Jones series had reached its definitive conclusion, the story of world-renowned archaeologist Indiana Jones passing into legend. Around 20 years later, though, the bull-whip-cracking adventurer returned with 2008’s Indiana Jones and the Kingdom of the Crystal Skull, a loving continuation of the Indiana Jones franchise.

Set in 1957, Indiana Jones and the Kingdom of the Crystal Skull finds a now older Indy (Harrison Ford) searching for a lost treasure in the South American jungle, partnering with his estranged son (Shia LaBeouf) and his former lover (Karen Allen). Released to mixed reviews in 2008, Indiana Jones and the Kingdom of the Crystal Skull remains one of the more polarizing entries in Indiana Jones’ canon, with many viewers taking issue with its sci-fi elements and action (especially the infamous scene where Indy survives a nuclear explosion by hiding in a refrigerator).

Though controversial among fans, Indiana Jones and the Kingdom of the Crystal Skull still boasts several interesting tidbits of information associated with its production. From discarded scripts to fascinating casting notes, here are some of the most intriguing behind-the-scenes facts about Indiana Jones and the Kingdom of the Crystal Skull.

Harrison Ford Performed Many of His Own Stunts

As with every Indiana Jones movie that came before it, Harrison Ford insisted he performs as many of his own stunts on Indiana Jones and the Kingdom of the Crystal Skull as possible, despite being 66 years old. As it happened, Ford had kept in such stellar shape since his previous work on The Last Crusade, and he did so without much fuss. To better prepare himself for the film, he spent an average of three hours a day at the gym, relying on a hearty diet of fish and vegetables to improve his physique. The regimen worked so well that the costuming department found Ford had the same size proportions as his earlier measurements on The Last Crusade.

Harrison Ford Insisted on Using His Iconic Whip Himself

Given the 20-year time lapse between the making of The Last Crusade and Indiana Jones and the Kingdom of the Crystal Skull, many tools in the world of filmmaking had changed in the interim since the previous Indiana Jones adventure, including new developments in stunt performances. Despite new safety requirements used on modern film lots, Harrison Ford insisted on wielding his character’s iconic bullwhip himself, overruling Paramount’s objections to the idea.

During the movie’s pre-production phase, Paramount suggested using a CGI whip instead of Indiana’s actual bullwhip. Ford – who’s always preferred practical effects over CG – called the suggestion “ridiculous,” training with the bullwhip for two weeks ahead of the movie’s production.

Harrison Ford Wanted To Insert More Jokes About Indy’s Age

Harrison Ford has always owned up to his age whenever he appears on screen. Rather than looking at it as something to be ashamed of, he prefers addressing it in the open, showing that people of advanced ages can still maintain their mental and physical faculties. With that in mind, Harrison Ford insisted the script include a more nuanced exploration of Ford’s age in Indiana Jones and the Kingdom of the Crystal Skull, even asking the screenwriter, David Koepp, to throw in a few more jokes regarding Indy’s expense.

Agreeing with Ford’s stance, Steven Spielberg also saw the potential for comedic quips to be inserted surrounding Indy’s age. “When a guy gets to be that age, and he still packs the same punch, and he still runs just as fast and climbs just as high, he's gonna be breathing a little heavier at the end of the set piece,” said Spielberg. “And I felt, ‘Let's have some fun with that. Let's not hide that.’”

Indiana’s Photo Collection Includes a Few Familiar Faces

After being dismissed from Marshall College, Indiana heads home and begins packing his bags, intent on leaving the U.S. and continuing his career in Europe. As he prepares to depart, he muses on photos of Marcus Brody – his former employer and close friend – and his father, Henry, who passed away before the film's events. As emotional as this scene is, a few other characters from the Indiana Jones series also appear in photos, albeit in a less prominent capacity as Marcus and Henry’s pictures.

In the background of Indiana’s house (shown in his scenes with Charlie and, later, Mutt), viewers can spot a few familiar faces from Indiana’s past adventures abroad. On the fireplace mantel is a photo of Sallah, Indy’s faithful companion in Raiders of the Lost Ark, The Last Crusade, and Dial of Destiny. On a small table is a photo of Henry and a young Indiana (River Phoenix, who played the character in the opening of The Last Crusade). And on the cupboard is a signed photo of Willie Scott, Indiana’s shrieking love interest in Temple of Doom.

Certain Characters Were Offered Cameos for The Movie

Indiana Jones and the Kingdom of the Crystal Skull distinguishes itself by featuring the first overarching connection to a previous Indiana Jones film, tying Indy’s romance with Marion in Raiders of the Lost Ark into the plot. In the film's early production stages, however, additional references to Indy’s past adventures were also planned, including a variety of cameos from former Indiana Jones cast members.

Sean Connery, in particular, was offered the chance to reprise his role as Indiana’s father, Henry Jones Sr., in a small cameo. After reviewing the script, Connery felt the character’s limited screen time was inconsequential to the film's plot, saying, “It was not that generous a part. And they had taken the story in a different line anyway, so the father of Indy was kind of really not that important.”

John Rhys-Davies, who played Sallah in Raiders of the Lost Ark and The Last Crusade, also decided against a cameo, feeling the character deserved a more prominent role. As Rhys-Davies recalled, “I was going to sit down, and then it would cut it into the wedding or something like Indy getting an award or something like that. I thought the character of Sallah is worth more to the audience than that.”

Fan-Favorite Characters From Star Wars and ET Make an Appearance

Throughout most of the Indiana Jones series, Steven Spielberg has habitually included easter eggs in past films he and George Lucas both worked on. In the case of Kingdom of the Crystal Skull, a few classic Star Wars characters appear in the lost city of Akator alongside a familiar face from one of Spielberg’s most famous films.

As Indiana and his companions traverse the mysterious South American temples of Akator, eagle-eyed viewers might notice the distinct designs etched into each tile on the temples’ walls. It might be difficult to see, but one of these tiles features the engravings of R2-D2 and C-3PO, the bickering droid duo who appear in every one of George Lucas’s six Star Wars films. A tile featuring the likeness of the title character in E.T. the Extra-Terrestrial also appears, further alluding to the alien motifs of Indiana Jones and the Kingdom of the Crystal Skull.

Shia Labeouf Had a Falling Out With Steven Spielberg After Filming

Though Shia LaBeouf jumped at the chance to work with his self-professed idol Steven Spielberg, the press junket for Indiana Jones and the Kingdom of the Crystal Skull proved harmful to the actor and director’s relationship. After the film was released, LaBeouf admitted to feeling responsible for the movie’s lesser quality compared to the first three films, saying in an interview with The Los Angeles Times, “I feel like I dropped the ball on the legacy that people loved and cherished.”

In response to these comments, LaBeouf said his friendship with Spielberg suffered. “He told me there’s a time to be a human being and have an opinion, and there’s a time to sell cars,” LaBeouf reflected. “It brought me freedom, but it also killed my spirits because this was a dude I looked up to like a sensei.”

Mutt’s Name Keeps in Line With a Series Tradition

Partway through the movie’s opening act, Indiana meets Mutt Williams, the ‘50s greaser he later learns is his son, Henry Jones III. Although Indiana expresses skepticism regarding Mutt’s nickname, the moniker references a long-standing tradition within the Indiana Jones universe.

In almost every Indiana Jones movie, a character named after a principal crew member’s dog appears in the film. Indiana’s name was taken from George Lucas’s Alaskan Malamute. Willie Scott’s first name was borrowed from Steven Spielberg’s Cocker Spaniel. Temple of Doom screenwriter Willard Huyck’s pet dog inspired Short Round's name. Seeing as “mutt” is an informal term for a dog of mixed breeds, Mutt’s nickname can be a reference to his mixed parentage. The character’s last name, Williams, is taken from John Williams, a frequent collaborator of Steven Spielberg and George Lucas, and the man behind Indiana Jones and the Kingdom of the Crystal Skull’s soundtrack.

George Lucas Modeled The Film After Classic Sci-Fi Films

With the original three Indiana Jones movies, George Lucas drew inspiration from the Republic B-serials of his youth, channeling his love for the niche adventure subgenre in creating the story and atmosphere of the initial trilogy. Given the new time lapse between The Last Crusade and Kingdom of the Crystal Skull, however, Lucas found it fitting to explore a new genre synonymous with the 1950s – that genre being the sci-fi film (like The Thing From Another World, It Came From Outer Space, and Invaders From Mars).

“It was the idea of taking the genre from the 1930s action adventure serials to the B science fiction movies of the early ‘50s,” said Lucas. “And I said if we move the whole thing into the ‘50s, which would be age appropriate for Harrison, that would be the cinematic equivalent, and I wanted to rest it on a cinematic antecedent like we did with the other one.”

Steven Spielberg Was Skeptical About The Movie’s Focus on Aliens

Despite Lucas and Harrison Ford’s enthusiasm for the project, Steven Spielberg hesitated to return to the Indiana Jones series, feeling the character’s journey had concluded with The Last Crusade. After much convincing from Lucas, Spielberg agreed to return to the series. Even as he signed onto the project, Spielberg expressed uncertainty regarding the movie’s inclusion of aliens as its main plot point.

According to Spielberg, when the idea was first broached in the 1990s, Spielberg felt the alien invasion film had been perfected by Roland Emmerich’s blockbuster smash hit, Independence Day. After Lucas persisted in pursuing the idea, Spielberg relented, going along with Lucas’s aspirations to introduce aliens in the film. Years later, Spielberg admitted the full extent of his indifference to the sci-fi elements of the movie. “I didn’t want these things to be either aliens or inter-dimensional beings. But I am loyal to my best friend. When he writes a story he believes in – even if I don’t believe in it – I’m going to shoot the movie the way George envisaged it,” said Spielberg.

The Finished Film Combined Multiple Drafts of The Script

Unlike previous Indiana Jones movies, where Lucas and Spielberg deliberated on several potential MacGuffins to use in Indiana Jones IV, Lucas had always settled on incorporating aliens early in the film’s production. As a result, most of the scripts written for Indiana Jones IV featured overarching similarities, with the final film condensing the various drafts into one cohesive movie.

The first draft of the script was written by The Fugitive’s screenwriter Jeb Stuart in 1993. Titled Indiana Jones and the Saucerman from Mars, it featured many elements later used in Indiana Jones and the Kingdom of the Crystal Skull, including Soviet antagonists, the Nuketown sequence, a tropical jungle, and Indiana Jones getting married at the film's end. The second draft, penned by The Last Crusade writer Jeffrey Boam, was completed in 1995 and included aliens, Indiana Jones’ son (named Abner in honor of Indiana’s mentor, Abner Ravenwood), and a reintroduced Marion Ravenwood. Frank Darabont wrote the third draft, featuring Marion and Harold Oxley, with Indiana’s son absent from the story. In the mid-2000s, David Koepp used these drafts to form the backbone for his script, with Spielberg, Koepp, and Lucas settling on the title Indiana Jones and the Kingdom of the Crystal Skull.

Mutt Was Planned To Be a Stereotypical Nerd

In earlier script drafts, Mutt Williams had a much different conception than the tough-talking greaser who later appeared in the film. In Jeffrey Boam’s 1995 draft of Indiana Jones IV, Mutt’s character was introduced as a bookish teenager named Abner, embodying the academic side of the Jones family tree (something that can be best seen with Indiana Jones’ father, Henry).

Though screenwriter David Koeep liked making Mutt a stereotypical ‘50s nerd, George Lucas decided against it. He wanted to make Mutt more brash and rebellious, paralleling Indy’s dynamic with his father. In The Complete Making of Indiana Jones, Lucas says, “[Mutt] needs to be what Henry Jones, Sr. thought of his son, and the curse returns to Indiana in the form of his own son. He's everything a father can't stand!”

Harrison Ford and Cate Blanchett First Met in Character

Having wanted to play a villain for years, Cate Blanchett joined the cast of Indiana Jones when she was offered the part of Dr. Irina Spalko, the film's main antagonist. To preserve an aura of mystery and eccentricity around her character, Blanchett proved elusive on the film set – so much so that Harrison Ford himself had trouble recognizing Blanchett out of costume.

“Two weeks into the movie, I'd only seen her in costume,” Harrison remembered. “She showed up one morning [in ordinary clothing] 'cause she wasn't working till later in the day, and I said, ‘Who's that?’” Ford, who had never met Blanchett before filming, admitted that he was impressed with Blanchett’s ability to disappear into her role as Spalko. “There's no aspect of her behavior that was not consistent with this bizarre person she's playing,” he observed.

The Movie’s Opening Sequence Is an Homage to George Lucas’s Youth

Spielberg and Lucas have always found a way to weave autobiographical elements into many of their films. In the case of Indiana Jones, the two are known for sprinkling in references to each of their youths. For example, the opening chapter of The Last Crusade was modeled after Spielberg’s time with the Boy Scouts, hence Indiana’s involvement in the group early on in his life.

When it came time for Indiana Jones and the Kingdom of the Crystal Skull, Spielberg chose to incorporate elements of Lucas’s own life and personal interests into the prologue of the movie. Given Lucas’s avid interest in cars and street racing (two things that pop up in Lucas’s iconic teen movie, American Graffiti), Spielberg decided to include a ‘50s drag race in the film's first five minutes.

A Few Vocal References Are Made to Sean Connery

While Sean Connery chose not to reprise his role as the taciturn Henry Jones Sr., a few references are made to Indy’s father throughout the film. As mentioned, a picture of Henry appears in Indiana’s study, leading Indiana to reminisce about his father to his friend and former employer, Charlie. In addition to this homage, the movie makes a few more references to the character.

Keeping in line with the idea that Indiana has inherited an estranged parental role to Mutt, Indiana adopts a handful of phrases favored by his father. This includes referring to Mutt as “Junior” – the go-to nickname Henry Sr. bestowed upon his son. In the diner scene when they first meet, Indiana also criticizes Mutt’s name, commenting, “What kind of a name is Mutt?” This feels like an homage to The Last Crusade’s ending, which sees Henry chastise Indiana for taking their pet dog’s name as his own. As they escape the Soviet camp in South America, Indiana can also be heard muttering, “This is intolerable!” another oft-used expression uttered by his father.