You're about to go see "Avengers: Endgame" and want to remind yourself about the subtle nuances of the Marvel Cinematic Universe (MCU), but you don't want to sit down for 40-plus hours and watch all 21 preceding films.

No one can blame you, and, frankly, you don't need to watch all of them. Who really wants to sit through "The Incredible Hulk" again?

If you feel you must have a refresher, or you have a friend who is new to the MCU, here are the seven must-see Marvel films ahead of "Endgame," in the order they were released. (Warning: Some scenarios that are potential "Endgame" spoilers will be mentioned.)

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"Iron Man" (2008)

This is the one that started it all. This is the origin story of the origin stories. This is the start of the Tony Stark-Pepper Potts relationship, which might play a role in "Endgame." Watch it again, and make sure to watch the credit scene to remind you how we first saw Nick Fury.

Also, if you're watching with a Marvel newbie, be sure to explain that the guy playing Rhodey is not the same guy playing Rhodey in "Endgame."

"The Avengers" (2012)

Our first look at all the Avengers together, but also how we learn about the Tesseract -- the first of the Infinity Stones. Also, leaked set photos from "Endgame" appear to show the actors re-creating the New York battle scene, so getting a refresher on what happened may be crucial. 

Again, watch the mid-credits scene as this is the debut of Thanos.

"Captain America: Civil War" (2016)

Captain America and Iron Man's friendship has been contentious from the moment they met. This is where you see it break apart like an iceberg in the  Antarctic. You'll need this reminder to prepare for the long-awaited reunion in "Endgame."

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"Doctor Strange" (2016)

Time travel is going to be a big deal in "Endgame" and the time loop at the end of this movie may play a part. You don't necessarily need to see the whole movie. If you need to save time, skip ahead to when Strange is first using the Time Stone.

"Avengers: Infinity War" (2018)

Obviously. This is the set-up for "Endgame." Get one more look at who died so you know who the Avengers will be trying to save.

"Ant-Man and The Wasp" (2018)

It's a pretty sure bet that the Quantum Realm and, perhaps, time vortexes will come into play in "Endgame," and both of these are addressed in this movie.

Can't say it enough. Watch the mid-credits scene. It's key.

"Captain Marvel" (2019)

She is going to be a big player in "Endgame," so find a theater that is still showing it and see it one more time. You may want to sit for the mid-credits here. The scene may be in "Endgame," but then again, maybe it won't. 

If you want to watch the movies in chronological order, go see this before watching "Iron Man."

The total run time for all these is a shade over 14 hours.

Avengers Infinity War Thanos
Thanos in Marvel's "Avengers: Infinity War."
Marvel Studios