"Right. Right. That is absolutely true," the Hank Pym actor said during a call to On Air with Ryan Seacrest when asked if the Ant-Man sequel is directly connected to the upcoming Avengers 4.
"I mean, all of them — I mean, the Quantum Realm, that's the key. That's the key," Douglas said. "The Quantum Realm plays an important part in all the next chapters, I think, of the Marvel films."
Ant-Man and the Wasp ended with Scott Lang (Paul Rudd) marooned in the world-between-worlds when he ventured inside to retrieve quantum energy intended to help cure Ava Starr (Hannah John-Kamen), a.k.a. "Ghost," who was left changed by the Quantum Realm's unleashed power.
Lang was left stranded when the freshly-reunited Janet van Dyne (Michelle Pfeiffer), Hope (Evangeline Lilly) and Pym were dusted by the Infinity Stone-powered snap enacted by Thanos (Josh Brolin) in Avengers: Infinity War that erased half of all life in the universe.
Janet, who was trapped in the Quantum Realm for decades, warned earlier in the film of dangerous "time vortexes," which have long been suspected to play a part in Avengers 4 as Earth's mightiest heroes work to undo the devastating effects of the snap.
Spoilery set photos previously revealed Lang somehow finds himself in the middle of the Battle of New York as seen in 2012's The Avengers, alongside a S.H.I.E.L.D. suit-sporting Tony Stark (Robert Downey Jr.) — suggesting the involvement of time travel, either by way of the Quantum Realm or the Time Stone last seen in the paws of the Mad Titan Thanos.
Marvel Studios chief Kevin Feige previously confirmed Ant-Man and the Wasp "connects directly to Avengers 4," adding, "These characters are going to be very important going forward."
A recent merchandise leak showed the Avengers suited up in what appear to be specialized costumes tailor-made for exploration in the Quantum Realm, resembling the suit worn by Pym when he ventured inside to retrieve Janet in Ant-Man and the Wasp.
"It's a whole other world, it's a whole other language and world, the Marvel comics world," Douglas told host Ryan Seacrest. "You gotta take a course in it, Ryan."
Ant-Man and the Wasp is now available to own on 4K Ultra HD and Blu-ray. Avengers 4 opens May 3.