Scarlett Johansson’sBlack Widowand Mark Ruffalo’sHulkmet on the big screen for the first time inThe Avengers, but a Marvel comic reveals Natasha Romanoff witnessed Bruce Banner’s Hulk transformation firsthand a while before that. Joss Whedon’sThe Avengersassembled Earth’s Mightiest Heroes in the MCU, allowing the team’s original members to interact after Phase 1 established each of their individual stories a couple of years before. Previously, Hawkeye was introduced alongside Thor in 2011’sThor, and Black Widow was introduced inIron Man 2alongside Nick Fury and Agent Coulson.
FollowingThe Avengers,Avengers: Age of Ultronrevealed thatNatasha Romanoff and Bruce Banner developed feelings for each othersome time between the Battle of New York and Ultron’s rebellion. Black Widow turned her fear of the Hulk into the Avengers' most effective tool to control the Gamma monster, as the best way to calm him down and turn him back into Bruce Banner was to have Black Widow talk to him. But while Bruce and Natasha’s story appeared to begin at the beginning ofThe Avengers, an official MCU comic reveals it had begun two years before.

The MCU’s Black Widow First Saw Bruce Banner Transform In The Incredible Hulk
The Avengers Prelude: Fury’s Big Week #5; Written By Eric Pearson and Christopher Yost; Art By Luke Ross, Daniel Hdr, Agustin Padilla, Wellinton Alves, Mark Pennington, Rick Ketcham, and Don Ho
The Avengers Prelude: Fury’s Big Weekfollows the events of the MCU’s Phase 1, encompassing the plot ofIron Man 2,Thor,The Incredible Hulk, andCaptain America: The First Avenger’s post-credits scene, all of which take place over the course of a single week in 2010.Fury’s Big Weekadapts major events from this point in the MCU’s timeline and presents a few details that Marvel Studios never acknowledged on screen. For instance, Nick Fury was heavily threatened to be replaced by the World Security Council just a few days before, and SHIELD kept Whiplash’s armor, the Destroyer, and Samuel Sterns' Gamma research in their archives.
As Fury and Coulson track Thor in New Mexico, Fury assigns Black Widow the task of keeping an eye on Bruce Banner, who gets intercepted by General Ross at Culver University.The Incredible Hulkfeatures Banner transforming into the Hulk and defeating Ross' forces at Culver, butFury’s Big Weekreveals that Black Widow was there all along.When Black Widow reports to Nick Fury, she looks visibly disturbed by the way Banner"changed,“as well as the fact that Emil Blonsky miraculously survived his injuries.

Black Widow’s Off-Screen Role In The Incredible Hulk Explains Her Fear Of Banner’s Alter Ego In The Avengers
Black Widow Was One Of The First MCU Characters To Witness Hulk’s Full Transformation
The Incredible Hulk’s opening sequence reveals thatBruce Banner’s Hulk transformation was already common knowledge to the authorities, but Banner was on the run and only transformed against his will while trying to hide from the military and ordinary criminals. Once General Ross closed in on him and Emil Blonsky attacked him at Culver, Banner’s full Hulk transformation finally became a public event, as several students and reporters filmed the Gamma monster’s rampage. At this point,Natasha Romanoff was the first Avenger to see the Hulk firsthand, which was probably a terrifying experience.
Natasha was scared to the point of tears when she recruited Bruce Banner, and she was unlucky enough to be trapped with Banner as he lost control when Loki attacked the Helicarrier

Being the only Avenger to witnessHulk’s full destructive potentialwith her own eyes, it makes sense for Black Widow to feel extremely nervous inThe Avengers. Natasha was scared to the point of tears when she recruited Bruce Banner, and she was unlucky enough to be trapped with Banner as he lost control when Loki attacked the Helicarrier. Fortunately for her, Banner regained control of Hulk and the two (or three, from Hulk’s point of view) developed a genuine relationship over the course of two movies.
Black Widow Was Involved In Hulk’s MCU Story From The Start
Natasha Romanoff Picked Up After Hulk’s Destruction Before He Met Her
The Avengers Prelude: Fury’s First Weekalso reveals that Black Widow was present in Harlem whenHulkfought the Abomination.Natasha Romanoff apprehended Samuel Sternsright after the Abomination attacked him and accidentally transformed him into the Leader.Captain America: Brave New Worldestablished that Thaddeus Ross forced an incarcerated Sterns to work for him for over a decade, which suggests thatBlack Widow’s behind-the-scenes influence onThe Incredible Hulkand the events detailed inThe Avengers Prelude. Fury’s First Weekare all official part of MCU canon.