The MCU has done a fantastic job of intertwining all their movies, including callbacks that, if you miss won't ruin the movie, but can add a whole new level for the true fan out there. Here are some things that were called back to in Avengers: Endgame.

And just in case you didn't realize until now, this is heavy on the spoilers. So if you haven't seen it yet, and don't want it spoiled TURN AWAY, SPOILERS BELOW!!

*
*
*
*
*
*
*
*
*
*

1. Budapest - Black Widow and Hawkeye mention Budapest while there on The Benatar (the Guardians of the Galaxy's ship). The two apparently had an interesting time in Budapest because it was brought up in the original Avengers.

2. "On your left" - After the Hulk snaps to bring back all those that were turned to ash from Thanos' original snap, just as Captain America looks defeated, he here's "on your left" in his ear piece. This is Sam AKA The Falcon, and it's a call back to when the two were jogging at the beginning of Winter Soldier.

3. Cheeseburgers - After Tony Stark's funeral, Morgan mentions to happy she wants a cheeseburger. Happy then tells her that her dad liked cheeseburgers. This is a call back to the original Iron Man when Tony is first brought back to the states and he's enjoying some burgers.

4. "We'll lose." "And we'll do that together too." - When Tony is saved at the beginning of Endgame, he brings up a conversation they had during Age of Ultron. During this conversation, Tony also points to the sky and says "That up there, that's the endgame." Oooooooo, foreshadowing.

5. "You should have gone for the head." - When the remaining Avengers show up to kill Thanos at the beginning of Endgame, Thor chops off his head. Rocket asks him "What did you do?" To which Thor replies, "I went for the head." This is a callback to the end of Infinity War.

6. "I can do this all day." - Captain America ends up running into his past self during the Chitauri siege on New York, and the past Cap make the comment "I can do this all day." Which is sort of Captain America's motto.