Trivia: When Thanos arrives at Titan, he is greeted by Doctor Strange, who is sitting down and playing with some rubble in his hand. When Iron Man, Thor and Captain America first see Thanos after he destroys the Avengers compound in Avengers: Endgame, he is similarly sitting down and playing with rubble in his hand. This could mean that Doctor Strange was mimicking what Thanos would do in the one out of 14,000,605 possible futures that he saw in which the heroes would defeat Thanos.
Trivia: Spoiler! Whilst Groot is turning to dust after Thanos activates the complete Infinity Gauntlet, he says "I am Groot" to Rocket just before he dies. James Gunn, writer/director of the Guardians of the Galaxy movies, confirmed via Twitter that Groot was actually saying "Dad" to Rocket before dying. (02:13:45)
Trivia: On Knowhere, Thanos is questioning The Collector, played by Benicio Del Toro, for the location of the Reality Stone. He asks him "Where is the stone?" at one point. This is a reference to a heist scene from the movie Snatch, in which Benicio Del Toro is robbing a bank and asks "Where is the stone?" with the same line intonation. (00:48:45)
Trivia: (SPOILERS) As a result of the shocking twist ending where half of the peoples of the universe disintegrate into nothing, Reddit organized a huge campaign where they would ban half the subscribers of the subreddit /r/thanosdidnothingwrong to answer the question "Who would survive if this actually happened and who wouldn't?" Directors Joe and Anthony Russo also signed up for the campaign. At the end of the campaign, over 300,000 people had their accounts banned, including Joe Russo.
Trivia: In this and other Avenger films, Bruce Banner (Mark Ruffalo) is depicted as standing much shorter than Tony Stark (Robert Downey Jr). In reality, Ruffalo is only one inch shorter than Downey (who is 5'9" tall); but Bruce Banner is always portrayed as a diminutive character in contrast to his gigantic Hulk persona.