Trivia: After Wade introduces his own avatar, it shows a line of people waiting by a portal. Just before Tracer shows up to the portal, you can see Sonic the Hedgehog standing towards the back of the line tapping his foot in the famous idle animation from the original game where he would tap his foot impatiently if the player left him standing still for too long. (00:04:55)
Trivia: When Dwayne Johnson signs to George to calm him down, he says "it's me." The sign he makes on those words is for "Rock," a reference to his stage name "The Rock." (00:15:25)
Trivia: Stan Lee makes his usual cameo as the guy that accidentally gets his car shrunk by Hope during the climactic chase. Sadly, this was the last Stan Lee cameo released before his death in November, 2018. (Although he had already filmed cameos for several other upcoming films before his death).
Trivia: When Rory is walking down the street wearing the Predator mask, there is a bright red/orange alien walking toward him. This is a nod to the original Predator costume that looked like a big bug, the red/orange color was used to film the stealth camouflage scenes. The bug suit was scrapped after a few test shots proved how silly it looked. Jean-Claude Van Damme was in the original costume, but he was let go when the costume was scrapped. (00:45:20)
Trivia: The $100 bill in the closing credits has the serial number DOT00002018. Which stands for Den of Thieves 2018, the year it was released. (02:24:00)
Trivia: The Anabelle doll from The Conjuring, another film of director James Wan, is visible while Mera is taking Arthur to her submarine ship. Blurry but there.
Trivia: Spoilers: There's a pretty subtle bit of foreshadowing in Gary's house. When he's seated and the group is playing Jenga, if you look behind Gary, there are two old-fashioned guns on the mantle. The way the shots of Gary are framed throughout the scene, both guns are pointed right at him several times. Later in the movie, Gary ends up being shot twice by two different guns - once by a gun loaded with blanks and once by a gun loaded with live ammunition.
Trivia: Warwick Davis plays one of the marauders. He also played Wicket the Ewok in Return of the Jedi.