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.
"Funny Aneurysm" Moment: Paul McCartney wrote "When I'm Sixty-Four" as a lighthearted song about a man who wonders if a woman will stay with him when he grows old. When Paul McCartney turned 64 in real life, his then-wife Heather Mills separated from him and they later divorced.
On a slightly more humorous note, over the course of his 64th year of life, Paul had that song played and sung to him so many times he jokingly said he regretted ever writing it.
Ringo Starr preferred The White Album and Abbey Road, but for more personal reasons—he claimed that he felt out of the loop and "like a session drummer" during the recording of Pepper, a claim that becomes particularly hilarious when you remember what teeth-pulling frustration and fighting took place during the next albums' recording sessions. (Regardless, many people consider "A Day in the Life" to contain some of his best work.)
Harrison's ambivalence over the album was ultimately for similar reasons to Ringo — given the emphasis on lush, orchestral psychedelia on the album, there wasn't a lot of call for his skills as a lead guitarist, and since he only had one written song on the album he was nudged to the sidelines a bit as well.
What Do You Mean, It Wasn't Made on Drugs?: Despite popular perception "Lucy in the Sky With Diamonds" is not actually code for "LSD"; it was about a drawing John's son Julian drew of his classmate Lucy (who he drew in the sky. With diamonds). Additionally, "Fixing A Hole" isn't about heroin, although Paul hasn't denied that it's about pot (in fact, he's more or less said that it is). It is quite likely, however, that "Lucy in the Sky" is about/inspired by an acid trip, and virtually certain that both of these were made on drugs.
"Fixing a Hole" seems to be in the film solely so George Burns, who otherwise only narrates, can have a song. There's no attempt to connect it to anything plot-related, and it isn't diegetic either.
The scene where SPLHCB go up in a hot air balloon, and it's implied that a plane crashed into it (we see it from the plane's point of view and then an explosion), and the band is now on the plane heading towards Hollywood. What??
The final Deus ex Machina appears to have no explanation, nor is one asked or expected by the characters.
You can make a compelling argument that this entire movie is this.
Nightmare Fuel: Mr. Mustard's fembots are incredibly disturbing. The fact that their biggest moment is singing "She's Leaving Home" does not help.
One-Scene Wonder: Earth Wind & Fire and Aerosmith only get one song/scene apiece, yet they're the best-regarded of the bunch. "Got to Get You Into My Life" has become one of EWF's signature pieces; some fans feel they perform it much better than The Beatles did.
So Bad, It's Good: Some sections of the film do have their fans — Steve Martin's take on "Maxwell's Silver Hammer" (lyrics not matching aside), Earth, Wind & Fire's "Got To Get You Into My Life", and the opening credits montage showing the original Sgt. Pepper and his band adapting to different musical styles from World War I to The Seventies, for instance.