The Avengers: Endgame trailer hints that Scott Lang may just be the hero the Avengers need to undo the Thanos snap. His appearance teases there is one way to bring back humanity, and that is through time travel.
The preview is full of Easter Eggs and clues that may very well reveal what happens in the film. One such clue is the appearance of the Ant-Man at the end of the trailer, which raises a question about his involvement in the film, particularly with the Avengers' mission.
His surprise appearance at the end of the Avengers: Endgame trailer suggests that he plays a key role especially since he has with him his trusty old van. Now, this is no ordinary van. Viewers may remember at the end of Ant-Man and the Wasp that he has transformed it into a makeshift laboratory equipped with a portal to the Quantum Realm.
The Quantum Realm may very well be the answer to undoing the Thanos snap. One way that the remaining Avengers can bring back their teammates and the rest of humankind is through the portal and possibly through time travel.
The end-credits scene in Ant-Man and the Wasp fuels this possibility. Right before Scott Lang traveled through the portal the original Wasp (Michelle Pfeiffer) warned him about entering a time vortex.
"Don't get sucked into a time vortex. We won't be able to save you."
Scott Lang may have done just that when he realized that there was no way he was getting out of the Quantum Realm with the help of his friends. After all, they too disintegrated, leaving him stuck inside. He may have taken the risk and entered the time vortex to escape. This seems like a logical reason enough to explain why he was there at the Avengers headquarters at the end of the Avengers: Endgame trailer.
To add fuel to this theory are the previous leaks that suggest the Avengers will be traveling back in time. According to Looper, the production recreated sets from the past Avengers films such as the Camp Lehigh in Captain America: The First Avenger, which was destroyed in Captain America: Winter Soldier.
This would explain why Steve Rogers is looking at an old photo of Peggy Carter in the Avengers: Endgame trailer since it was at the camp where they first met, and he was probably going to find her there too. Captain America also has his old suit on, which he needs to wear if he has to blend in and not mess up the time stream.
Regardless, fans will know how the heroes can undo the Thanos snap when Avengers: Endgame hits theaters on April 26, 2019.
