
It appears that Avengers: Doomsday may feature a third major character from the Thor movies. A new social media post from Kat Dennings has fans theorizing that Darcy Lewis could be the latest beloved MCU fan favorite to join the fight against the diabolical Doctor Doom (Robert Downey Jr.).
The hypothesis stems from a new photo Dennings shared on her official Instagram account, in which she can be seen proudly holding Captain America's shield. "Don’t get excited, I was just sampling the hardware," Dennings wrote in the caption.

Darcy began her MCU career as an intern/assistant to astrophysicists Jane Foster (Natalie Portman) and Erik Selvig (Stellan Skarsgård). In addition to appearing in Thor, Thor: The Dark World, and Thor: Love and Thunder, she was also a major part of the Disney+ series, WandaVision, and a key player in multiple episodes of What If...?
Darcy's Potential Role in Avengers: Doomsday
Although there are several ways in which Darcy could play into the events of Doomsday, it's those What If...? appearances that provide the most tantalizing hints as to her potential role in the latest Avengers adventure.
Season 3, Episode 4 of the program, "What If... Howard the Duck Got Hitched?," found Darcy in an unexpected romance with none other than Howard the Duck (voiced by Seth Green). After getting married, Darcy lays an egg during the convergence of the Nine Realms (an event central to the plot of Thor: The Dark World). As a result, we learn, the human/duck hybrid that will eventually hatch from that egg is destined to have incredible powers.
Consequently, a cavalcade of the MCU's most important characters - including Nicky Fury and SHIELD, Yondu Udonta and the Ravagers, the Grandmaster, the Dark Elves, the Frost Giants of Jotunheim, and even Thanos and his Black Order - attempt to obtain the egg for their own benefit.
Despite this, Darcy and Howard manage keep hold of the egg, which eventually hatches their daughter, Byrdie.
Byrdie subsequently reappeared to play a key role in the series' two final episodes, "What If... The Watcher Disappeared?" and "What If... What If?". In these chapters, she's an adult (voiced by Natasha Lyonne) and a member of the Captain Carter-led Guardians of the Multiverse, who eventually help to save Uatu from the Order of the Watchers. in the Observational Plane with Uatu to mourn Carter's death. Byrdie and the other Guardians were last seen with Uatu in the Observation Plane.
Given that Doomsday will be the culmination of the MCU's Multiverse Saga, it's not a stretch to imagine that Byrdie could ultimately play a part in the epic battle against Doctor Doom... in which case, it's logical to assume that her mother would somehow be involved.
Every Thor Character Confirmed and Rumored for Avengers: Doomsday
Assuming Dennings is indeed in the cast of Doomsday, Darcy joins several other luminaries of the Thor films.
Thor
Thor himself, Chris Hemsworth, was confirmed as a member of the Doomsday cast back in March. He has since been seen in a behind-the-scenes photo with some of the film's other stars, including Channing Tatum, Simu Liu, Paul Rudd, Vanessa Kirby, and Robert Downey Jr. Thor was last seen in Thor: Love and Thunder, which concluded him with adopting Love (Hemsworth's actual daughter, India Rose Hemsworth), the biological offspring of Gorr the God Butcher (Christian Bale). Hemsworth and Downey will be the only actors to have appeared in all five of the Avengers movies. Recent videos shared by Hemsworth on YouTube suggest that Doomsday could mark his swan song as the God of Thunder.
Loki
Like Hemsworth, Loki actor Tom Hiddelston was part of Doomsday's initial cast announcement earlier this year. We last saw the God of Mischief at the conclusion of Loki Season 2, in which he saved the multiverse by holding all of its many branches and becoming Yggdrasil, which connects the Nine Realms in Norse mythology. Thus, Loki became the God of Stories and the new protector of the multiverse. Given this, it's not hard to imagine how he'll play into the events of Doomsday.
Valkyrie (rumored)
Although Valkyrie hasn't been officially announced as part of Doomsday's ensemble, actress Tessa Thompson was recently spotted with Pedro Pascal near where the film is shooting. Pascal, of course, will play Mister Fantastic, Reed Richards, in both Fantastic Four: First Steps and Doomsday. When we last saw Valkyrie in Love and Thunder, she was the ruler of New Asgard, which also became a haven for Skrull refugees in The Marvels.
Avengers: Doomsday will be released on December 16, 2026.