This film has a lot in common with Pretty in Pink (reviewed here), coming from the same writer (John Hughes) and director (Howard Deutch) and some similar themes.
Mary Stuart Masterson is brilliant in a role vaguely similar to Jon Cryer’s in Pretty in Pink (but far less goofy). That is, she's a bit of a social outcast secretly in love with her best friend of the opposite sex. Her character is a lifelong tomboy who plays drums, dresses in masculine clothes, and is rumored around school to be a lesbian.
The best friend (Eric Stolz) is a quiet, good-looking fellow student with a talent for art who works nights at a service station and annoys his father by putting off seriously planning for college. He’s infatuated with Lea Thompson, a beautiful girl from his working-class neighborhood but who’s so attractive she runs with the popular kids and dates one of the richest guys in school.
Thompson, hugely popular after Back to the Future, was approached by Deutch early on, but she disliked the part and initially turned it down.
At about this time, if I’m not mistaken, her new big-budget film was released, one that like Pretty in Pink featured a character called (at least by Thompson), “Duckie.” The film in question was a pet project of executive producer George Lucas, who expected it to be a tremendous hit that would pay off the mortgage on his Skywalker Ranch complex. But as you may recall, Howard the Duck didn’t quite work out that way. (Lucas reportedly told people at the time that in 20 years Howard the Duck would be hailed as a masterpiece. Well, it's been over 20 years, George.) Lucas’s friend Steve Jobs helped him out financially by buying the Lucasfilm computer animation division, which Jobs later renamed Pixar.
After Howard the Duck, Thompson was more receptive to a role in Some Kind of Wonderful, especially since Hughes had in the meantime rewritten the script to make her character more sympathetic, and director Howard the Deutch still really, really wanted her for the part, as for that matter did co-star Eric Stolz.
Stoltz had already co-starred with Thompson in Back to the Future, in which Stolz played Marty McFly. If you don’t remember it that way, it’s because after more than a month of shooting he was replaced by Michael J Fox. Thompson and Stolz were still friends, which turned out to be helpful since Stolz and Howard Deutch didn’t get along and Thompson was able to mediate.
Incidentally, I suspect one reason Deutch was so persistent in trying to get Thompson for the part is that he had a crush on her. If so, it worked out well for him, because she dumped Dennis Quaid to start dating Deutch and later ended up marrying him.
Thompson won an award for her acting in Some Kind of Wonderful, but I was more impressed by Mary Stuart Masterson. Of course, it helped that she played such an interesting character, one with flaws (she’s unnecessarily cruel to a male classmate who’s attracted to her, for example) but who cares so much about Stolz that she ends up trying to help him make a good impression on Lea Thompson even though it’s breaking her heart.
Several other actors and their roles merit mention, including John Ashton (whom you’ve likely seen in several movies playing a cop) as Stolz’s father, Maddie Corman as his little sister, and in particular Elias Koteas as a skinhead bully who ends up being not such a bad guy after all and pretty funny besides. He routinely ignored the script and direction and made up his own lines and actions, but he was so hilarious he got away with it. At one point he surprised Lea Thompson by laying his head on her shoulder to her obvious amusement, and they kept it in the film.
Incidentally, Maddie Corman had auditioned early on. When she was called back for a meeting her mother had just been diagnosed with terminal cancer, and because her mother so wanted her to get the part, she came back from the meeting saying, a bit prematurely, that they’d given it to her. Her mother was delighted by the news. By the time she was cast for real, her mother had died. Corman is really good in the role, funny, cute, believable, and likable.
I won’t describe the ending except to say that I liked it a good deal better than the one for Pretty in Pink, so I don’t have to bore the dickens out of you describing how I'd rewrite it.