In the first Back to the Future movie, Marty McFly encounters many hurdles throughout his time-traveling adventure in 1955 Hill Valley, including repairing Doc Brown’s DeLorean, fighting Biff and his friends, and ensuring his parents fall in love at the “Enchantment Under the Sea” dance while jamming out to Chuck Berry. However, one thing that’s absent from the 1985 film is Marty’s aversion to the word “chicken,” an iconic plot point introduced in Back to the Future Part II that would come to define Marty’s entire character in the future.

Despite only coming into play nearly halfway through the trilogy, Marty’s refusal to back down to “chicken” became a defining characteristic of the denim-clad skateboarder, whose signature line “Nobody calls me chicken” becomes one of the staples of the Back to the Future series that appears in (almost) every film. While the first film largely focused on Marty’s efforts to get back to 1985, the Back to the Future sequels needed to introduce new conflict within Marty’s psyche, and what better place to start than with the prideful adolescent’s insecurities and ego?

Back To The Future Part II Introduced “Chicken” Because Marty McFly Needed A Character Flaw

The First Film Focused On George’s Character Arc, Not Marty’s

Per a CinemaBlend interview with screenwriter Bob Gale, the idea for “chicken” came from the desire to give Marty a character flaw for him to overcome in the Back to the Future sequels. Since Marty is shown to be easily provoked in the first film, it wasn’t a large jump for the screenwriters to then “verbalize” his explosive nature, according to Gale:

Well, when it came time for us to do the sequels, we realized that we needed to give Marty a character flaw that he was going to have to correct. And we didn’t really establish a real character flaw in the first movie because the character who experiences growth in the first movie is George McFly. But we did establish Marty’s a bit of a H๏τhead, and that it seems like he’s kind of quick to mix it up with Biff in the scene in the school cafeteria and the scene in the café when Biff just kind of towers over him. So we thought, ‘You know what? Let’s use that.

This allowed Gale and director Robert Zemeckis to set up a fatal flaw for Marty, which ultimately leads him to get into a disastrous car accident that ruins his music career dreams after Needles goads him into a dangerous drag race—that is, until he successfully overcomes his pride in Back to the Future Part III and resists taking the bait when Needles calls him “chicken.”

In short, since the first Back to the Future focused so much on George McFly’s arc, the sequels had to set up Marty’s fatal pitfall in order for the time-traveling teen to resolve his emotional arc at the end of the trilogy.

Back To The Future’s “Chicken” Line Is Different From Other Running Gags In The Series

Marty Has Real Character Development In Part II And III

What makes the “chicken” line different from the rest of the recurring gags in the Back to the Future series is that it wasn’t included from the start. The rest of the callbacks—including Marty always waking up to a version of Lorraine (Lea Thompson), Doc Brown’s “Great Scott!” catchphrase, and Biff always ending up in manure—were all set up in the first film, and their inclusion in the following sequels set up the franchise’s theme of events repeating themselves throughout history.

Despite being added late in the series, the “Don’t call me chicken” line has become nearly as iconic as the rest of the recurring gags in the Back to the Future series, namely because it’s always fun to root for a flawed hero as he navigates overcoming his fatal weakness. Furthermore, the “chicken” line is much more than just a running joke in the trilogy—it’s true character development, and by resisting the urge to fall into the same old trap, Marty completes his emotional arc at the end of the third film.