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.
His eventual romance with Laura. Did it happen out of nowhere due to Steve being an Entitled Nice Guy who eventually badgered Laura until she gave in? Or was there subtle foreshadowing in episodes where Laura would find herself missing him or jealous of his attention to another girl, or moments where she went out of her way to stand up for him at the risk of losing a prom date or her own popularity?
The anti-bullying episode is probably the most egregious example. Midway through the episode, it morphs into an anti-gun episode. An interesting thing about the "Save A Life" campaign is that a DJ plays what are supposedly "everybody's favorite rap/hip hop tunes." Do you remember what was popular at the time?
Another example would be the episode where Eddie reveals to his classmates that he's a virgin. The idea that Eddie and Steve would be the only two kids in their high school who have never had sex notwithstanding, are we really supposed to believe their classmates would ridicule them for it? Especially since after this episode, the issue was never mentioned once.
Base Breaker: Steve. Depending on who you asked, he was either the best thing about the show and elevated it from being just another family sitcom to greater heights than anyone could have dreamed of, or he was an obnoxious creator's pet who ruined the series by taking screentime away from the Winslows, the real main characters. Alternately, there are some who think that he was kind of funny but worked better in small doses.
Broken Aesop: Steve is just one big walking Broken Aesop. Does he truly promote being yourself, or does he promote refusing to change, as he continues to behave childishly well into his teens? Laura once defended him from a Jerkass date saying Steve always respected her despite the fact that he was constantly invading her home without her permission (or her family's for that matter), refused to back off despite how often she told him she wasn't interested in him, took even the smallest act of kindness from her as a sign that she actually did reciprocate his feelings and that he was "wearing her down", and more than once basically chased off prospective boyfriends of hers. In other words, he was basically stalking her.
Creator's Pet: Some fans believed Steve was this over time since he has taken up most of the show and leaving the other Winslows out of the spotlight.
Ensemble Darkhorse —> Breakout Character: Steve was initially meant to be in the show for one episode, but his popularity led to him becoming a recurring character. Eventually, he would end up the star of the show. During the first season, completed episode scripts were rewritten just to include Steve.
Eddie's friend Waldo was hugely popular, only to just never show up once they made the channel hop to CBS.
Also worth noting is Waldo started out as a delinquent before becoming one of Eddie's best friends.
Myra was introduced as a romantic false lead. Much like Steve before her, she charmed the audience and was promoted to the main cast.
Fail O'Suckyname: Alfred Looney, the school janitor (ah, that's Loo-NAY; it's French), Steven Q. Urkel, and Carl Otis Winslow, given the fact that his initials spell COW. Plus, he's overweight, so that makes it even worse.
Family-Unfriendly Aesop: For many, Steve's relentless pursuit of Laura and eventually getting engaged to her sounded like "stalk your dream girl long enough, and she'll one day give in."
At least three episodes of the show dealt with the evils of gambling. Two of them did so quite reasonably. In one, Steve and Eddie got cleaned out by a pool shark, and threatened ("gambling can leave you broke, and even lead to threats of bodily harm"). In another, Steve won a watch with great sentimental value from Carl's boss in a poker game, but then gave it back to him, explaining that he played for fun, and didn't want to take something that meant so much to him ("you can destroy other people by gambling, but in moderation, it's ok"). In the final one, though, Steve and Eddie went to an illegal casino in which they won $32,000, which the casino was clearly both capable, and perfectly willing, to pay but then the casino was raided by the police ("things are immoral not because they harm you or someone else, but because the state says so"),
Steve basically bragging that he's still a virgin and revealing that Eddie is too. It's apparently supposed to be a positive message regarding abstinence, but Steve just revealed something that he had no business even knowing—he learned this by eavesdropping on a private conversation between Eddie and Carl—and even if he did, he certainly had no business revealing it to a locker room full of people.
"Funny Aneurysm" Moment: Any time Myra (post breakup with Steve) makes any comment about not wanting to live without him. Michelle Thomas (the actress who played Myra) died at the age of 29 from a rare form of stomach cancer.
Growing the Beard: Happened somewhere around the third season, when they figured out how to use Steve without him sticking out like a sore thumb.
Hilarious in Hindsight: Myrtle Urkel is regarded as odd for wearing vintage clothing from the 50s and 60s, among other things, now with the wide interest in vintage clothing and websites selling such wares, along with the popularity of series like Mad Men or Masters Of Sex, Myrtle would be regarded as some sort of fashion plate or be given a job as a model for such websites or a job on the sets of Period Piece films and shows!
Informed Wrongness: Pretty much any time one of the other main characters gets mad or annoyed at Steve when he does something stupid or insensitive, even if its Innocently Insensitive. For example, the time Steve accidentally trashed a model ship Carl had worked hard on. True, it was an accident but still, Steve, as usual, forced himself into the Winslow home without their permission. Through his usual lack of respect for their personal space, he ended up destroying a piece of Carl's property, causing Carl to grumble "You know, I really hate that kid." This upset Steve so much that he started sleepwalking into the Winslows home and assaulting Carl out of resentment. And yet, Carl is made to feel like he's the bad guy even though it was Steve who was at fault.
Another time, Steve took Carl to court to sue him for accidentally killing Steve's pet stick bug. When asked to take the stand to explain himself, Carl's response was, "Ladies and gentlemen... it was just a stupid bug."
Jerkass Woobie: Myra. She's a clingy jealous girl of the worst kind, becomes increasingly batshit crazy in later years and eventually resorts to breaking the law to keep her hooks in Steve. And yet you can't help but feel sorry for her whenever you're reminded that underneath all the crazy, she really does love him.
Waldo certainly qualifies, as well. Like Steve (although to a much lesser extent), he tends to annoy nearly everyone on the show (even Steve himself), but he's loved by fans.
Myra. A lot of people like her more than Laura, despite her annoying Abhorrent Admirer status on the show.
What an Idiot: Most nerdy guys would have killed to have a girl like Myra throw herself at them, but instead, Steve continued to woo stuck-up and uninterested Laura who only agreed to date him in the last season. But then again, Myra was rather batshit-insane.
The Woobie: Steve, even as annoying as he can be, doesn't deserve half of the crap he goes through.