Continuity mistake: When Marcus sees his baby grandson, a nurse in the background is picking up a white diaper. In the close-up the diaper is now blue. (00:03:35)
Continuity mistake: At the arena, when Scooby's blue suit bursts, the ground is covered in small blue pieces that disappear in the following shots.
Continuity mistake: SPOILERS: During the final scene, when Samuel L. Jackson is "puppeted" to lift his arm up to make it look like he's pointing a gun at the SWAT team, the number of laser-sights visible on his chest changes between cuts. In the wide-shot, there's only three, but when it punches into a close-up, suddenly there are five.
Character mistake: The Rufus hologram states that he first brought the phone booth to the Chosen Ones (Bill and Ted) in 1989, referencing events of the original film. While that was the year the first movie came out, it took place in 1988 (indicated by the opening title card and dialogue throughout the movie).
Factual error: Smaller pieces of the comet start raining down in a highway setting. While small fragments of a comet can come down, they'd all be traveling at anywhere between 20 miles per second as the comet is an extra-solar comet. Those small pieces wouldn't make such piddling explosions, they'd be creating concussion waves that would rupture your organs and send vehicles flying. The heat even from those small rocks would ignite all foliage within 50-100 yards. (01:31:00 - 01:34:00)
Continuity mistake: A pile of drugs gets blasted up with powder flying everywhere yet there's none on the ground seconds later.
Other mistake: In The Croods, Guy was handing out bananas and gave one to Grug, which he threw away. But in this film, he does everything to get this mystical fruit that he hasn't had since his childhood.
Continuity mistake: The girl that wanted her bully in high school to be tortured filmed the torturing with an iPhone XR then was later holding an iPhone X before the movie ended.
Factual error: SPOILERS! While the ending of Al being arrested for murder at his own wedding is dramatic and cathartic, it wouldn't have happened that way. There's no way that the cops would have known to search the wooded area near the cabin; they would have needed to find physical evidence linking the cabin to Al; they would have needed to establish that Al had no alibi for the time in question; etc. None of that would have happened that quickly or that quietly.
Other mistake: The email that starts it all for Sid Straw, the announcement from the University of Pennsylvania that he has been chosen to serve on the reunion planning committee, starts off with a nonsensical sentence that no one from U Penn would have ever typed. It's obviously the product of a studio runner whose work no one bothered to proofread. (00:01:15)
Continuity mistake: When the girls are standing on the beach with the flares to guide in the German aircraft they are in two rows just a few metres apart. The view from the aircraft shows them much further apart, wide enough for the aircraft to land between them.
Visible crew/equipment: The diner flashback has possibly one of the worst handling of extras ever. The lady behind Crystal Fox keeps glancing at the camera and playing with her food in very unnatural fashion, but it's the guy with glasses behind Mehcad Brooks that truly shines; throughout the scene he drinks from an empty glass and, even more obvious, eats invisible food from his fork, usually throwing a glance right at the camera every time he does so, looking like he's about to crack into a laugh at the absurdity of it. It's such a bad performance that one really wonders if he was trolling Tyler Perry or something. (00:32:25)
Other mistake: The Volvo the woman is driving has a front Oregon license plate numbered 643 ODS, but her rear license plate is 902 CSM. (00:02:55 - 00:03:45)
Other mistake: In the credits of the movie, the creator of the original comic's name is misspelled as "Bob Macleod" when it should read "Bob McLeod."
Factual error: The USMC Embassy Guard is an enlisted Marine Sgt. He is wearing a Commissioned USMC Officer's cover (hat) that has gold braid and gold oak leaf motifs on the visor. (01:20:15)
Continuity mistake: Tim is showing the Nanny's phone to the others. He plays the message from his parents, but does it tapping the bottom part of the touchscreen, while the media file and its "play" button as established in previous views, is at the top. Likewise, when he turns towards Jane asking "Do you want to be taken care of?" he is pointing at the bottom of the device, but in the reverse shot his finger is at the top. (00:43:30)
Factual error: The soldiers had 506 Regiment's helmet markings of the 101st Airborne, and on their sleeves the 82nd Airborne and 1st Division shoulder patches.
Continuity mistake: Look at the forehead of the hotel manager. Everytime he raises his eyebrows, you can see his prosthetic forehead piece.
Revealing mistake: During the dance number in the airport, Santa grabs a security guard who then starts break dancing. It's obvious this dancer is a stunt double as he's younger and skinnier than the real guard.
Other mistake: Vaughn was sleeping in the back seat of the van with his head leaning on Gina's shoulder. When the collision occurred, his body somehow straightened up and went head first between the front bucket seats, through the front windshield, and he was ejected/killed. Based on his sleeping position in the van, he should have rolled forward and been kept in the back seat by hitting the front seats. A sleeping person is also less likely to be injured/killed because the body doesn't stiffen preparing for impact. If the accident actually happened as portrayed in the movie, Vaughn's body should have had visible cuts and be covered in blood, not just have a small amount of blood coming out of the side of his mouth. (00:07:53)