Avengers: Doomsday star hails the Russos' "special sauce" after admitting he was originally "not convinced" that the Marvel crossover could juggle its massive cast

Avengers: Doomsday and Thunderbolts* actor David Harbour has praised directors Joe and Anthony Russo for their guiding hand in bringing the madness and chaos of several big-name actors together for the Marvel crossover.

When asked by Screen Rant about how the Russos manage to bring scenes together, including when actors aren't on set, Harbour (who plays the Red Guardian in the MCU) responded, "I was not even convinced when we started, and this movie's gonna be really good. They have a special sauce."

Harbour, who last appeared as the Russian superhero in Thunderbolts*, added, "I don't even really understand, but they just know how to do these things… there's something about the layers in which they put the comedy and the drama and the surprises and the scale and the epicness and all that stuff. It's incredible."

The Russos returned to the MCU after a spell away from the cinematic universe, a period which saw them direct the likes of The Gray Man and The Electric State for Netflix, plus Apple's Tom Holland-starring Cherry. They had previously directed Captain America: The Winter Soldier, Captain America: Civil War, Avengers: Infinity War, and Avengers: Endgame – and they currently rank among the highest-grossing directors of all time.

Meanwhile, Harbour is joined in the Doomsday cast by his fellow Thunderbolts* members, including Florence Pugh, Sebastian Stan, and Wyatt Russell. There's even speculation that Chris Evans could be joining the full list of Avengers: Doomsday cast members, all thanks to the ex-Captain America actor suspiciously returning to Steve Rogers-level shape in recent weeks.

Avengers: Doomsday hits cinemas on December 18, 2026. Still playing catch-up? Dive into our guide on how to watch the Marvel movies in order.