WARNING: The following article contains spoilers for Avengers: Endgame, in theaters now.
Despite its heavy themes, Avengers: Endgame has a lot of fun exploring more than a decade of the Marvel Cinematic Universe. The remaining heroes use the Quantum Realm to travel back in time, exploring familiar settings, from 2012's The Avengers, 2013's Thor: The Dark World and 2014's Guardians of the Galaxy, while maneuvering old battles and reuniting with lost friends. It's natural, then, that the blockbuster sequel had fun with unexpected cameos, with many former MCU actors making appearances.
That's in addition to cameos by Thanos creator Jim Starlin, and the late Stan Lee, in his final MCU role. Here are the biggest surprise cameos in Avengers: Endgame.
Frigga & Howard Stark
The Quantum Realm permits some of heroes to gain closure with people they've lost, with Thor and Tony Stark each speaking to a departed parent while in the past. Rene Russo's Frigga didn't receive much attention in her only previous appearance, in Thor: The Dark World, sharing scenes with Loki (Tom Hiddleston) and Jane Foster (Natalie Portman), but never spending much time with her son Thor before she died at the hands of Malkeith and Kurse. Endgame gives Thor one last chance to talk with his mother in an extended scene in which she tells her son to rediscover himself.
Jon Slatterly also returns, in his fourth appearance as Howard Stark, following Iron Man 2, Ant-Man and Captain America: Civil War. He's always held a certain power over his son, but speaking to each other almost as equals strengthens Tony's resolve going into the final act of Endgame.
Jane Foster
Natalie Portman appeared as Jane Foster in the first two Thor films, serving as the romantic lead. But despite a few references in Avengers: Age of Ultron and Thor: Ragnarok, she disappeared from the MCU. That's due in part to conflicts the Oscar winner had with the studio during the production of Thor: The Dark World.
Thor and Rocket Raccoon travel back in time to recover the Aether (Reality Stone) from Jane during the events of The Dark World, and sneak into Asgard. While most of the focus of the sequence is on Thor speaking with Frigga, and coming to terms with his failures, Rocket goes off to extract the Infinity Stone from Jane. There's a quick shot of Jane rising out of bed and walking away as Rocket sneaks up from behind.
Sitwell & Barlow
Captain America must recover the Mind Stone, contained within Loki's Scepter during The Avengers, from Hydra sleeper agents Sitwell (Maximiliano Hernández) and Brock Rumlow (Frank Grillo), aka Crossbones. Both are still masquerading as S.H.I.E.L.D. operatives at this point, and Captain America isn't looking to start an unnecessary fight.
The scene is an extended homage to Captain America: The Winter Soldier, with Rogers catching them at the elevator. But instead of duking it out with the agents, like in that 2014 film, Steve Rogers uses his knowledge of the future to his advantage: He deceives Sitwell by whispering "Hail Hydra," and claims the Mind Stone without a fight.
Alexander Pierce
More surprising than Sitwell and Barlow is the cameo by Robert Redford as Alexander Pierce, the mastermind of the events of Captain America: The Winter Soldier. Although he was killed at the end of that film, the Hydra leader was still undersecretary of the World Security Council in 2012, when the events of The Avengers occurred.
Surrounded by S.H.I.E.L.D. agents, Pierce demands the Space Stone and custody of Loki from Tony Stark and Thor after the Battle of New York. However, the Ant-Man and Tony Stark from the future defuse the situation by simulating a heart attack in the past version of Iron Man. It's a brief cameo, but it depicts Pierce trying to acquire an Infinity Stone for himself, and ties the events of The Winter Soldier to those of The Avengers.
The Ancient One
Tilda Swinton has the most substantial cameo, reappearing as the Ancient One. She has actual impact on the plot, certainly more so than Jane Foster or Alexander Pierce. The reason the team heads back to New York during the events of The Avengers is that not only were the Mind and Space Stones in the area, but so was the Sorcerer Supreme. Hulk goes looking for Doctor Strange, and finds the Ancient One instead. While Frigga can discern that Thor is from the future, and quickly moves on, the Ancient One has an extended conversation with Hulk about his mission.
She explains the concept of alternate realities to the heroes (and by extension, the audience), and sets up the film to feature characters from different time periods moving freely and going to war with one another. She also convinces Hulk they need to return the Infinity Stones to their original places, to prevent dark ,alternate timelines. Her best moment comes from her seeming awareness of her successor, Stephen Strange, as she mentions he will "become the best of us."
Harley Keener & Thaddeus Ross
By far the most surprising cameos come during the funeral of Tony Stark, at the end of the film. Besides obvious attendees such as Happy Hogan, May Parker, Nick Fury and Maria Hill, there are also surprising appearances. Among those in the back of the ceremony is Thaddeus Ross, longtime enemy of the Hulk and played by William Hurt. He was one of the primary antagonists of The Incredible Hulk before briefly appearing in Captain America: Civil War and Avengers: Infinity War. Considering how few references there are to The Incredible Hulk, it's a nice touch.
Iron Man 3 also gets a handful of shoutouts in the film. During the final battle with Thanos and his army, Rhodey wears Iron Patriot armor into battle after War Machine is damaged. Harley Keener (played by Ty Simpkins) also makes a reappearance, after only showing up once before. Keener was the boy in Iron Man 3 who helped Tony Stark get back on his feet. He even received a lab from Tony, so it's nice to see the kid (now considerably lankier) at the funeral.
Jarvis
The loyal butler to Howard Stark and the eventual inspiration of Tony's AI assistant, Edwin Jarvis is actually a first for the MCU. Played by James D'Arcy, he makes a brief appearance after Tony talks with his father. Howard's driver, her greets his employer and convinces him to brush off the encounter with Tony.
Jarvis is actually the character solely from television to appear in an MCU film. While Nick Fury, Maria Hill, Lady Sif and, most notably, Phil Coulson, appeared on Agents of S.H.I.E.L.D., none of the characters introduced in the Marvel television series has made the leap to the big screen before this. Jarvis was central to the short-lived Agent Carter series, where he often acted as a bit of a sidekick to Hayley Atwell's Peggy Carter, who also returns for Endgame.
Directed by Joe and Anthony Russo, Avengers: Endgame stars Robert Downey Jr. as Iron Man, Chris Evans as Captain America, Mark Ruffalo as Bruce Banner, Chris Hemsworth as Thor, Scarlett Johansson as Black Widow, Jeremy Renner as Hawkeye, Brie Larson as Captain Marvel, Paul Rudd as Ant-Man, Don Cheadle as War Machine, Karen Gillan as Nebula, Danai Gurira as Okoye and Bradley Cooper as Rocket, with Gwyneth Paltrow Pepper Potts, Jon Favreau as Happy Hogan, Benedict Wong as Wong, Tessa Thompson as Valkyrie and Josh Brolin as Thanos.