Hair

In 2008, I won't even use the word "mul let" because it's the worst joke since the 1990's. But the hair styles are truly feeling residual cutural dusting from the late 80's. I don't know that this was an accurate depiction of teenage life or just an exaggeration, but either way, it's an impressive display. 

We also see the start of the Andrea crushin' on Brandon theme that would linger / annoy the audience through the first three seasons (at least). We also see the politically correct climate creeping in, another 90's quotient. 

The scene where Kelly sits outside to eat with Brenda was recycled almost to a tee in Clueless, the 1994 flick that led to the inevitable late 90's teen movie revival. I never made the connection or importance of BH 90210 to those movies, but it makes sense when you put it together.