Following the first Avengers: Endgame teaser, fans have been exploring numerous theories about how the Avengers and the rest of the universe's heroes will be trying to undo Thanos' snap. Time travel has become one of the most discussed options, with many wondering if it'll be the Quantum Realm; Captain Marvel's cat, Goose; the Time Stone; or some other device Robert Downey Jr.'s Tony Stark cooks up that does the trick.
As for those who are looking for a more conventional approach to the Mad Titan, and who don't believe temporal roaming will factor in, well, one key scene from Infinity War may bolster the theory that our heroes will indeed be traversing the timestream.
The Infinity War Hint
When Tony is in Central Park with Pepper Potts, he's discussing having a family. He goes about it in a roundabout way, nervously and very much afraid of such a future commitment.
However, he tells her about his dream where they had a baby, Morgan, named after Pepper's uncle. Of course, this was interrupted by Doctor Strange and Bruce Banner, kickstarting Tony's trip to Titan and the current chain of events where he ends up marooned in space with Nebula trying to get back home.
But while many see this as a fleeting moment with Tony feeling the need to settle down even more, what if the dream about Morgan is actually the sign that time travel has already occurred?
The Multiverse Exists
This is because the dream may not have been a dream at all, but a memory from the future, or more so, an alternate future where Tony and Pepper have Morgan. The speculation is that Tony and Pepper get married and have a baby, but it doesn't happen in this current timeline of the Marvel Cinematic Universe. It's actually from a timeline where Infinity War never takes place, Tony never gets lost in space and Morgan is born.
Now, how exactly does Tony get this memory? Well, it's due to a causal loop, which is a time travel paradox where a future event (the heroes traveling back in time in Endgame and stopping Thanos from ever getting the Infinity Stones) is the cause of a past event (which means the Mad Titan never comes to Earth and Tony gets to marry Pepper), which then causes a future event to occur (Morgan's born to the happy Stark family).
Both realities would then exist in space-time continuum, but their origin cannot be determined, as one cannot occur without the other. This is why the ripple effect is felt with actual experiences from the new reality (i.e. baby Morgan being born) seeping over into the one we know at present (where Tony receives his "dream").