After Adam is stabbed in the eye by his girlfriend, he has a nasty wound. In later scenes the wound is missing.
When they are playing "quarters" in their room at the hotel (in the present), the number of drinks on the table change.
In the scene where the guys encounter the ski patrol for the first time. Jacob is pushed down and the Ski patrolman's hand radio clearly falls in the snow. In the next shot it's back in his chest pocket.
Lou starts off with 6 shots of tequila, he throws one it breaks, he throws another it breaks but he still has 5 shot glasses left.
When the guys are discussing what they did in 1986, the knee patches on Lou's pants go from open to closed between shots.
As it is the Hot Tub which is the time machine, and the characters entered it naked, their items such as i-phone, drink and snowboard should not have traveled with them.
The AFC Championship game played on 11 January 1987 shown in the bar was between the Denver and Cleveland. However, the game took place in Cleveland rather than Denver as shown.
They are watching the AFC Championship game depicting the Denver Broncos vs. the Cleveland Browns with the Browns winning with the game commentator claiming the "Dawg Pound is going to the Super Bowl", which is a reference to Cleveland.
The ski lodge is having Winterfest '86, and the NFL Playoffs are on TV so it has to be January and it must be the 1985 NFL season. The Denver Broncos did not make the playoffs that year, the Browns were eliminated in the divisional round by the Miami Dolphins, and the New England Patriots represented the AFC in the Super Bowl that year losing to the Chicago Bears. Furthermore as of this post (Oct. 2021) the Cleveland Browns have never been to a Super Bowl.
The ski lodge is having Winterfest '86, and the NFL Playoffs are on TV so it has to be January and it must be the 1985 NFL season. The Denver Broncos did not make the playoffs that year, the Browns were eliminated in the divisional round by the Miami Dolphins, and the New England Patriots represented the AFC in the Super Bowl that year losing to the Chicago Bears. Furthermore as of this post (Oct. 2021) the Cleveland Browns have never been to a Super Bowl.
Snowboarding was developed in the United States in the 1960s, and the first USA National Snowboard race was held near Woodstock, Vermont in 1982, so it wouldn't have been odd to see one on the slopes in 1986.
When the time travelers return to 1986, they discuss doing everything the same so as not to mess anything up in the future. One person says "If you step on a bug, the Internet won't be invented." The Internet was already invented in 1986, but not widely known or used in public homes. Moreover, these guys are from 2010 and will not necessarily know - then and there - when exactly the Internet was invented, so it would not be out of character for them to think that in 1986 Internet still had to arrive.
Lou is seen betting on Denver against Cleveland in the 1986 AFC Championship Game. While the actual Broncos-Browns game did take place in January 1987, it could be reasonably referred to as the 1986 conference championship because it followed the 1986 regular season (for example, even though they won Super Bowl XX in January 1986, the champions of that year are always called the "1985 Chicago Bears").
At the start of the film when Jacob can be seen playing a PC game for about two seconds you can clearly see the Windows Media Player 11 "play" buttons as they come up when a video is full screen and has the mouse over it.
The 1987 AFC Championship Game was the early game with a kickoff time of 12 p.m. Eastern Time. In the movie the game was on at night.
(at around 1h 02 mins) After the end of the scene where Jacob sees the repairman at the cigarette machine, the next scene opens with Nick still passed out and leaning against the side of a urinal. After Nick wakes up you can see a smudge of his makeup on the side of the urinal for the rest of that scene.
Towards the end of the movie as the three guys are talking to Phil and he is handing them the map printout from Lougle, you can see two search options underneath the address search bar and the option for "Search the Web" is checked instead of "Search the Maps" option.
When the one armed bell boy assists in taking everyone's bags to the room when they first get there, when he reaches to grab the bags you can clearly see the outline of his arm, that supposedly doesn't exist, under his shirt.
The end of the movie implies that Lou stays behind to take advantage of his knowledge of the future. He appears to now be the lead singer for Motley Crue, but Vince Neil was already a solid member of the band and had been a founding member since 1981. It is highly unlikely that Lou was able to dethrone Vince from the band.
In the film Blaine mentions "21 Jump Street" but the TV series didn't start until 1987.
When Nick Weber is in the hot tub with the groupie (allegedly in 1986) They're listening "Push It" from Salt-n-Pepa but this song wasn't released until March 9, 1987 and advanced into the Top 40 the week of December 26, 1987.
The movie is set in early 1986, yet one of the anti-communist 'jocks' at the ski resort makes reference to 21 Jump Street (1987), a show that didn't begin airing until 1987.
When Adam is writing poetry in the room after the breakup, he is listening to "I Just Died In Your Arms tonight" by the Cutting Crew. This song wasn't released in the U.S. until the spring of 1987.
One of the snowmobiles being used by the ski patrol was not available for sale until 1997 by Ski Doo.
You can clearly see a poster for Rambo III (1988) on the wall of Blaine's bedroom. Rambo III wasn't released until 1988. They travel back to 1986.
When the bellhop falls on the ground and the chainsaw lands in his armpit, when he gets up you hear a noise like the ripping of clothing. But when he gets up and raises his arm, there is no rip in his armpit.
When Adam is doing drugs after breaking up with Jenny, he takes a hit from his bong and says "hungry" but his mouth doesn't move.
It is stated at the beginning of the movie that Jacob is 20. Since he was conceived in 1986, that would put "present time" at 2006 or 2007. However, the hot tub is clearly set to "2010" when the guys return to the present.
When the time travelers return to 1986, they discuss doing everything the same so as not to mess anything up in the future. One person says "If you step on a bug, the Internet won't be invented." The internet was already invented in 1986, but not widely known or used in public homes.