These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Hot Tub Time Machine
Big Lipped Alligator Moment: Jacob is running to find his companions. Suddenly he is dancing with a girl and asking if he can text her. The girl is never seen or mentioned again.
The girl does show up in a deleted scene, in which she asks Jacob about his snowboard. The scene of them dancing makes a little more sense after watching the deleted scenes.
Critical Research Failure: Motley Crue's "Home Sweet Home" was already released in 1985; a year before it would have been possible for Lou to create the song.
The recording shown is from a live show, it's more implied that he somehow took over the band and changed the name possibly due to his great song ideas thanks to his future knowledge.
A poster for Rambo 3 is seen on Blane's bedroom wall, despite the film being set over two years before Rambo 3 was released in May of 1988.
Poison performing at Kodiak Valley is seen as a big deal and April is covering the band for Spin Magazine, but in 1986 Poison had not yet achieved mainstream fame (that wouldn't happen until 1987).
Blaine references 21 Jump Street when he's arguing that the mains are Commie spies, but that didn't debut until 1987.
There's also the revelation that Lou is Jacob's father.
Family-Unfriendly Aesop: The gang using their knowledge of the future for their own personal benefit results in all of them having much better lives than they did before.
Well, the movie has a stronger adherence to Rule of Funny as opposed to any moral.
Harsher in Hindsight: Adam's quote: "One little change has a ripple effect and it effects everything else. Like a butterfly floats its wings and Tokyo explodes or there's a tsunami, in like, you know, somewhere".
Jerkass Woobie: Lou when he calls out Adam for being such a poor friend and never being around when he needed him. After a brief argument, Adam gives in and admits that Lou's got a point.