As well as marking the formation of a new superpowered MCU team, 2025’s Thunderbolts is also speculated to introduce a new hero to the franchise. Speaking recently to David Finch (via YouTube), The Walking Dead and Invincible creator Robert Kirkman revealed that Steven Yeun, his frequent collaborator and star on both shows, had been to a costume fitting for the Sentry in Thunderbolts. This seemed to confirm pre-existing rumors that Yeun would portray the Sentry in the MCU, and this introduction could create a firm connection between Thunderbolts and another highly-anticipated Phase 6 project, Fantastic Four, as Marvel’s First Family has a strong relationship with the Sentry in Marvel Comics.

Thunderbolts Is Now Releasing After Fantastic Four

Thunderbolts’ previous release date of July 26, 2024, is now occupied by Shawn Levy’s Deadpool 3, which is set to be the only MCU feature film releasing in 2024. Captain America: Brave New World, Thunderbolts, and Blade have all been pushed back due to 2023’s WGA and SAG-AFTRA strikes, with the latter two now releasing as part of Phase 6, after Fantastic Four. This means that Steven Yeun’s debut as the MCU’s Sentry will occur after Marvel’s First Family has been introduced to the MCU, and potentially even create the opportunity for members of the Fantastic Four to appear in Thunderbolts, and there is precedence for this in Marvel Comics.​​​​​​​

Sentry & Mister Fantastic Are Best Friends In Marvel Comics

Robert Reynolds was introduced in Marvel Comics’ The Sentry #1 in 2000 as an Everyman character who wakes up one day suddenly remembering his previous exploits as a superhero, the Sentry. Years prior, a drug-addicted Reynolds had consumed an experimental super-soldier serum in an effort to fuel his addiction, but this serum shifted his molecules an instant ahead of the current timeline, gifting him the power of a million exploding suns, making him one of the Marvel Universe’s most powerful heroes. Throughout his career as a superhero, he formed close bonds with many other notable characters, including the Hulk and Reed Richards, a.k.a. Mister Fantastic.

After Reynolds’ reawakening, the Marvel Universe’s other heroes begin to remember his existence, too. Reed Richards, the elastic leader of the Fantastic Four, remembers that the Sentry was his best friend, with the Golden Guardian of Good having teamed up with the Fantastic Four for many adventures. The world’s memory of the Sentry, including Reynolds’ own memory of his superhero career, was erased by Doctor Strange once they realized that the Sentry’s archenemy, the Void, was actually the other half of Reynolds’ own personality. Hence, nobody remembered the Sentry prior to 2000’s storyline, but once the world begins to remember him, his friendship with Reed Richards is once again explored.

The Sentry had joined the Fantastic Four on various adventures.

While both superheroes are remembering their previous friendship, they learn that the Sentry had joined the Fantastic Four on various adventures. Robert Reynolds had helped the Fantastic Four battle their iconic archenemy, Doctor Doom, Reed Richards was Reynolds’ best man at his wedding to his wife Lindy, and Richards was pivotal to the Sentry’s plan to save the world from the Void by wiping everyone’s memory. The Sentry’s initial storylines in Marvel Comics displayed some inspired narrative twists, retconning a powerful hero – referred to as the most powerful superhuman by Richards – into the complex history of the Marvel Universe, and this could also occur in the MCU.

Reed Richards In Fantastic Four Sets Up A Stronger Story For Sentry In Thunderbolts

The new release schedule of the MCU’s Phase 6 means Fantastic Four will now release before Thunderbolts, and before the Sentry’s debut. This means that Reed Richards will be established in the MCU before Steven Yeun makes his first appearance as Robert Reynolds, and though it’s unclear whether Marvel Studios will follow Marvel Comics’ history for the Sentry, it’s possible that this narrative could unfold in Phase 6. Pedro Pascal has been rumored to be the MCU’s Reed Richards, and the dynamic between Pascal’s Mister Fantastic and Yeun’s Sentry would be interesting to explore, and while this likely won’t take place in Fantastic Four, Thunderbolts​​​​​​​ will present the perfect opportunity.

The dynamic between Pascal’s Mister Fantastic and Yeun’s Sentry would be interesting to explore.

Steven Yeun’s Robert Reynolds could debut in Thunderbolts having just remembered his past as a prominent MCU superhero, which could constitute cameo appearances from several heroes in the Phase 6 team-up movie. Following his debut in Fantastic Four, Reed Richards may make his next appearance in Thunderbolts, greeting Robert Reynolds and learning about their past friendship. Since Fantastic Four won’t be an origin story, this would be a great way to flesh out the backstories for both of these prominent Marvel Comics heroes, better establishing them as part of the wider MCU, even though they will have only just debuted in the franchise.

Will Sentry Have A Future In The MCU After Thunderbolts?

Although Robert Kirkman may have let the cat out of the bag regarding Steven Yeun’s casting in Thunderbolts, this hasn’t yet been confirmed by Marvel Studios, so this could change. The Sentry’s potential debut in Thunderbolts also doesn’t give any hints to his potential future in the MCU, though since he’s a key member of the Avengers in Marvel Comics, and takes part in iconic storylines such as Civil War, World War Hulk, and Siege, it’s possible the Sentry could appear in the MCU’s adaptations of these plots. Marvel Studios has introduced several overpowered heroes in recent years, and the Sentry’s Phase 6 debut could add another to the list.

During a March 2023 interview with Empire, Steven Yeun revealed that he was convinced to join the MCU’s Thunderbolts as he wanted to work with director Jake Schreier again. The pair previously collaborated on the Netflix series Beef. The fact that Yeun hadn’t shown interest in joining the MCU prior to Schreier’s hiring as Thunderbolts’ director may suggest he could be hesitant to continue in the MCU’s future without Schreier, implying Thunderbolts may be a one-time-deal. This would be a dire shame, as the Sentry could deliver some of the most impactful and emotional storylines and relationships in the MCU, so deserves to be a permanent fixture of the franchise.