These are the best, most satisfying, fan-service callbacks to the Marvel Cinematic Universe in 2019's Avengers: Endgame. As the highly-anticipated culmination of over 20 fan-favorite films, it only makes sense that the Russo brothers would cram in as many references and tie up as many loose ends as possible to other films in the MCU, like Teen Harley from Iron Man 3, cheeseburgers from the original Iron Man, on your left from Captain America: The Winter Soldier, and many more. Which callback was your favorite? Are there any we missed? Let us know in the comments!Check out more awesome Avengers: Endgame content from WatchMojo here:Top 10 Things You Missed in Avengers: Endgame: