In honor of 90210 Day -- think about today's date -- we're taking a look back at the original stars of "Beverly Hills 90210" and how they've changed since the show debuted 20 years ago in 1990!

From Kelly Taylor to Dylan McKay, check out the OG students of West Bev.

Can you guess whose handsome man mug got a not-so-subtle scramblin'?

It's been a couple weeks since we've seen 'em, but yesterday in Studio City, Kellan Lutz reminded us that his ridiculous abs still exist.

Ironic since earlier this week, the "Twilight" star told Us Magazine "By no means do I want to be a piece of meat for the rest of my career. It's funny when you get asked to do a talk show, and then they follow it up with requesting you take your shirt off"

Looks like he still wouldn't take much convincing.

Olympic god Michael Phelps showed off his skills in the pool ... mackin' on his on-again/off-again GF Miss California USA Nicole Johnson at the Grand Wailea in Maui yesterday.

We're told Phelps took a bunch of photos and signed autographs for fans ... in between gettin' real close and personal with Miss Cali.

The dude has got game.

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It's the car that abs bought -- a 2008 Bentley coup for The Situation, and all he had to shell out was around $100,000.

But Sitch isn't rollin' alone ... his brother, Marc Sorrentino, got a slightly less-expensive 2008 Bentley.

Our Sitch sources say both cars were paid for through the brothers' company -- MPS Entertainment ... brokered by Andy Eminger from Celebrity Rental.

We're told the boys are getting the cars suped up with custom rims and sweet sound systems.