If you only have time to watch one movie before "Avangers: Endgame," this is the holy grail. It will give you the quick rundown on everything you need to know about the Infinity Stones, Thanos, and every character you may not be familiar with as the Avengers meet the likes of Doctor Strange and the Guardians of the Galaxy for the first time. Watch Avengers: Endgame Online

If you don't know who is alive and who was dusted at the end of "Infinity War," then this is a no-brainer. Last year's movie also gives you a big hint as to why Nebula may have been spared in the Thanos snap. If the Avengers are going back in time, Nebula's the only person left alive who knows where to find the orange soul stone her father collected in "Infinity War." Official Avengers Endgame Twitter