In Thor: Love & Thunder, Chris Hemsworth’s Thor comes face to face with somebody he once loved. Sure, there’s his ex-girlfriend Jane Foster (Natalie Portman), who makes her return as the Mighty Thor, but Thor also reunites with another ex — his hammer, Mjölnir. Thor is delighted to have the repaired hammer back in his life, but his joy causes some friction between him and his new weapon, the ax Stormbreaker that he forged in Avengers: Infinity War. Stormbreaker is jealous and acting out, and according to director Taika Waititi, it’s Groot’s fault. 

Speaking at a press conference attended by SYFY WIRE, Hemsworth explained how Stormbreaker’s jealousness emerged organically while shooting the upcoming film. 

“The ex-girlfriend turns up dressed as him, that's a shock,” Hemsworth said of Jane’s unexpected return. “And all of the sudden the weapon that he held so dear for so many years now belongs to someone else. And then he has Stormbreaker, who starts to sense a little jealously there. So, that kind of evolved through the film, didn't it? I don't think it was in the original script, but it was fun.”

Waititi then jumped in with an explanation for why Stormbreaker — an apparently semi-sentient weapon — would act up when faced with a potential rival from Thor’s past.   

“I don't know if this is the way anyone else thought about it, but you gotta remember Stormbreaker's made of Groot's arm — well, you know, the handle is,” Waititi said, referencing the forging of the weapon as seen in Avengers: Infinity War. “Groot was like a teenager when he did that. So we felt like Stormbreaker was young and had only just been born about five or six years ago. It had to feel a little bit like an adolescent and like it was going through changes.” 

“It was having mood swings,” Hemsworth added. 

While Stormbreaker is no longer a part of Groot, it makes a certain amount of sense that the weapon would take after his co-creator. As seen in the post-credits scenes of Guardians of the Galaxy vol. 2 and more fully in Infinity War, the teenaged Groot is indeed a teenager.  

Without spoiling anything (indeed Hemsworth looked to Marvel Studios president Kevin Feige for permission to discuss Stormbreaker’s jealousy before talking about it to the press, lest he incur Marvel’s famously anti-spoiling ire), the dynamic between Thor and his ax is one of the funnier bits in Love and Thunder. It is, however, based on some actual character drama that previous Thor films had clearly established. As Korg (Waititi) said in Thor: Ragnarok, Thor had “a pretty special and intimate relationship with this hammer and that losing it was almost comparable to losing a loved one."

You can see why Stormbreaker might be jealous. 

Thor: Love and Thunder opens in theaters on July 8. 

Thor: Love and Thunder is one of many big blockbusters expected to light up the box office this summer. Jurassic World Dominion is out now, and Jordan Peele's sci-fi horror mystery Nope opens July 22 in theaters.