Will spends half the series in high school and half in college.
In the episode "Money For Nothing" Carlton says he's a pro when it comes to weird gambling combinations and Will remarks "Why does Michael Jackson hang out with the kid from Home Alone?" This looks like a random pop culture joke, but we learn in a Halloween episode that Macaulay Culkin is Carlton's idol. Will was probably asking him a legit question.
In "Six Degrees Of Graduation" Will mentions he has no future in music. This could be a reference to the fact that Will Smith started out as a rapper and getting in debt with the IRS actually got him on Fresh Prince.
Ashley's changedbehavior in seasons 3-6 was more than just her becoming a teenager, but rather due to both Will's influence over her and her jealousy over not being the baby in the family anymore. She unintentionally learned from Will that in order to get attention, you need to act out. Granted, within the first few seasons, he basically told her that she was allowed to have a mind of her own, which in itself is a great thing to learn, especially at an early age, but given his eventual Flanderization, she was bound to behave like he did.
"The Young and the Restless" has Phil being very overprotective of his mother and we are left to assume that it's because she had a cold. Early next season, it is revealed Phil's father died a year before which would place the former episode about a few months after his dad's death. This could explain why Phil was so terrified for his mother, he could've thought the cold could've been an early sign of impending death.
In "Will Is From Mars", Will is completely unfazed by George Jefferson's insult about the former's father. While it could just be a deadpan reaction to a Cloudcuckoolandery old man who's just talking random smack, Will's father actually did show up in the previous season... but ultimately turned out to be such an unsympathetic deadbeat — of course Will has no reason whatsoever to want to stick up for the guy (and, in fact, probably mentally agrees with George)!
In early seasons, Will was described as being a good student, but around season 3 his performance as a student took a dip. It seems like Early Installment Weirdness on the surface but not so much if you use a little imagination. Season 3, Will was a senior in high school and as many high school seniors can attest to, your grades do slip a little your senior year as you lose motivation to do well. Princeton stated his grades "Would make an impressive batting average". Given Princeton's exceptionally high standards Will could have an overall average of a B+ or A-, which isn't Princeton level good but still good nonetheless. And as far as nearly failing his music class in the season 3 finale, "The Ethnic Tip" from season showed Will can get bad grades occasionally, and it also ties back into the senioritis issue. Once he got into college, being Brilliant, but Lazy can get you through high school just fine but poses a lot of issues in college.
At some point, Uncle Phil was about to sit on Will and Will yelled out "Oh lord mercy, No!". It is true that Phil being a large man, it would hurt, but given how he already sat on Will, Carlton and Hilary when Will needed surgery, Will knew exactly what was in store for him if he did sit.
"Geoffrey? Get me one of those stick thingies." This line from "Banks Shot" is meant to convey that Phil isn't very experienced with playing pool. However, he reveals in the rematch that not only is Phil the superior pool hustler, but he also has his own high-quality custom cue. The line is a Stealth Insult toward the inferior quality of the cues furnished by the pool hall compared to Lucille, and toward Phil's opponent by extension for using them.
In "Asses to Ashes", Will tells a story about how he unfairly won a competition to go out with a girl by using a two-headed coin in a heads-or-tails toss and uses this as proof that "nice guys finish last". In this very same episode, Judge Robertson, Phil's sexist and corrupt former mentor dies from a stroke brought about due to his careless lifestyle, is insulted at his own funeral and Phil ends up taking his job as a judge. Will's guilt over the judge's death could also be a result of him realizing that his own bad habits could catch up to him.
Jackie Ames, Wills childhood friend from Philly, was a recurring character in the first couple of season four episodes only to disappear afterwards. It makes more sense when you remember that she came to ULA on a Basketball scholarship. Meaning she wouldnt have enough time to run the Peacock and juggle her schoolwork, practices, games, etc.
One episode has Will trying to convince a girl to sleep with him and gets Jazz to help him do so by staging a fake wedding so that she'll be with him while thinking that they're married. He doesn't end up following through out of guilt though. It seems bad enough thinking about it just as a con, but it could also qualify as something called rape by deception and in if he had slept with her, Will could have been in a whole lot of trouble.
In "Its A Wonderful Lie", Will catches Ashley in a frathouse bedroom at a college with a 19 year old football player. Will and Phil are already disgusted by Ashley's behavior, and rightly so, but it gets even more scarier, for the football player, as Ashley is stated by Will to be 15 years old. That's right, regardless of whether Ashley gave consent or not, this is blatant statuatory rape. Its a miracle Phil didn't press criminal charges.
They never actually stated the guy was 19, just that he was in college. There's actually a loophole in the law stating that once you turn 18, legally you can be with a person three years younger than you. So if the guy was 18 (therefore a college freshman) while extremely creepy, would still technically be legal and therefore free him of charges.
Two relating to Judge Robertson:
It is stated by Phil that Robertson was a decent and reasonable man before becoming a corrupt and sleazy judge. In "Robbing the Banks" it seems that Phil has become more callous to the plight of those less fortunate than himself after taking the now dead Robertson's place as judge, suggesting that it was the job that made Robertson the way he was. It's disturbing to see how much more like Robertson Phil could have become especially when you consider they both suffered from unhealthy lifestyles which killed Roberston and nearly killed Phil as well.
At the end of "A Night at the Oprah", it is stated that Robertson has adopted 12 youths from the ghetto to increase his poll numbers. What became of those kids after Robertson died is never mentioned.
Whenever Uncle Phil screwed up, he was Exiled to the Couch. Problem is the family lives in a friggin' mansion. There weren't any guest rooms he could have slept in instead? For that matter, why did Will and Carlton have to bunk together whenever there were guests? Again, there weren't any guest rooms that the guests could have stayed in?
My guess it it's indeed a big house, but not exactly a mansion (given the Geoffrey takes care of the place single-handed rather than a larger staff) and the bedrooms are similarly big and when Will moved in he got the only guest room. Between the people that already live there before Will moves in there are at least five bedrooms (Phil and Vivian, Hillary, Carlton, Ashley, and Geoffrey) plus the guest room that became Will's bedroom.
There was always the pool house, as seen in later seasons.
Since it's punishment from his wife, I'd expect the reason being that he'd make the situation even worse if he did sleep in a real bed?
In "Sooooul Train" it was mentioned Uncle Phil was staying in the pool house after a particularly bad fight, and Aunt Viv didn't seem to mind