It may have arrived in theaters just six weeks after Iron Man, but ever since then The Incredible Hulk has been regarded as the unwanted step-child of the Marvel Cinematic Universe that the studio would rather you didn’t acknowledge. In fact, if it wasn’t for the recent return of Thaddeus Ross, then the events of the entire movie could technically be wiped from canon without affecting the franchise in the slightest.
Besides the appearance of Robert Downey Jr.’s Tony Stark in a brief post-credits sequence that was blatantly tacked on to provide some sort of connective tissue, The Incredible Hulk was almost completely devoid of any mentions or references to the wider MCU other than the obligatory Stan Lee cameo. However, a new Easter Egg has been discovered that offers a subtle connection to Captain America: The First Avenger, which wouldn’t even be released until three years later.
In The Incredible Hulk, the super-soldier serum given to Emil Blonsky that turns him into Abomination is labeled as having been developed by a Dr. Reinstein in a blink-and-you’ll-miss-it shot. While that might sound like a throwaway ‘generic evil scientist’ name in the grander scheme of the MCU, it’s actually an incredibly obscure reference to Captain America’s origin story that even diehard comic book fans would be forgiven for failing to have noticed.
As it turns out, in the pages of Marvel Comics, Dr. Reinstein was actually an alias once used by a certain Abraham Erskine, who was of course instrumental in both the recruitment of Steve Rogers and the creation of the formula that turned him into a superhero in Captain America: The First Avenger. This only goes to show the incredible level of background detail put into virtually every frame of the MCU, even in movies like The Incredible Hulk that were soon swept under the rug and almost entirely ignored for the next decade.