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.
Harsher in Hindsight: Max and Alex have a conversation in "Blood Brothers" after Alex gives a blood sample to cover for Max, even though he doesn't know why. When they refuse to tell him the truth, Alex says they screwed up his life, and Max claims he's trying to protect Alex. If Alex hadn't discovered the truth, he wouldn't have died.
Hilarious in Hindsight: David Conrad plays Agent Pierce, an MIB-type who believes aliens are a threat and wants to get rid of all aliens to protect the planet. Fast forward about fifteen years, where he plays Ian Quinn, who is utterly opposed to MIB types (and would probably want to exploit the aliens to make a buck off their gifts, danger to the planet be damned.)
Hollywood Homely: Would three kids looking like that really go unnoticed at a high school that long? Only if they're on a teen drama, where everybody everyone who gets Character Focus looks that good.
Tess, Michael, and Maria are the most widely disliked, but for different reasons.
Shocking Swerve: In an utterly bizarre turn, the show introduced a character as their new math teacher, who raised Liz's suspicions by getting a simple mathematical concept wrong and being strangely inquisitive. Eventually it was revealed that she's not really a teacher, she's actually a .... guidance counselor? What. Why would their guidance counselor be impersonating a teacher?
It turned out it was because she wasn't a guidance counselor, either. She was an FBI agent. The "guidance counselor" thing was probably an improvisation when she screwed up her "teacher" cover.