4.Speaking of not smiling, Wilmer Valderrama looked like was he thrilled to be there, while his That's '70s Show co-star Mila Kunis looked adorable.
5.Ashton Kutcher looked like he came in his That '70s Show character, Kelso.
6.NSYNC showed up in a whole lot of synthetic shiny clothing and frosted tips.
7.America's third favorite boy band, 98 Degrees, arrived in coordinating outfits.
8.Tatyana Ali looked pretty in lavender.
9.Alyson Hannigan looked like she was channeling Garbage's Shirley Manson.
10.And she took a moment to pose with her American Pie co-star Jason Biggs.
11.Steven Tyler was there too (along with his Aerosmith bandmate Joe Perry), bringing "cool mom" vibes to the show.
12.While Freddie Prinze Jr. brought some goofy dad realness.
13.Christina Aguilera somehow managed to work both a large belly chain and pink pleather cheetah print skirt.
14.Monica sparkled (literally, she looks she rolled around in gold glitter).
15.While her "Boy Is Mine" duet partner, Brandy, looked chic in white.
16.Sandra Bullock and her then-boyfriend Matthew McConaughey were flirtatious backstage.
17.Tyra smized for her life.
18.TLC (or at least two-thirds of them) looked thrilled to be there.
19.Beverly Hills, 90210's Luke Perry and Ian Ziering were probably there to receive a lifetime achievement award for playing teenagers for like 15 years.
20.Jennifer Lopez looked flawless (like always).
21.Sarah Michelle Gellar looked kick ass (of course).
22.Tyrese zipped up his pants after almost flashing the camera.
23.Rachel Leigh Cook was all that.
24.Jordan Knight was there after reclaiming teen idol status with his solo hit "Give To You."
25.Blink-182 brought the love.
26.While Britney Spears brought pink disco ball pants.
27.Jennifer Love Hewitt, the unofficial teen queen of 1999, showed up in every late '90s girl's dream prom dress.
28.And she reunited on the red carpet with LFO, whose video for "Girl on TV" she starred in.
