This episode is hilarious but not quite classic. It falls just short of that.
During his the pyramids scenes, Joey walks the line between endearingly dumb and irritatingly stupid. "Paper, snow... a ghost!" is funny both times but bringing it up afterwards wasn't all that funny to me. But I would say that the pyramids scenes ascend in quality. The last one is really funny -- and Joey's fumble at the end -- calling his partner's list of supermodels "women Chandler could never get" is top-notch. His pyramids partner is a good choice too, actually -- he's so absolutely straight, and even though you can sense his irritation with Joey, it's subtle enough that Joey completely misses it.
Phoebe's bachelorette party is a hoot, although I'm a little confused as to why Rachel and Monica really chose the tea pary in the first place. It was a lovely party, but it just wasn't very... Phoebe. Hence mini-stripper. Jennifer Aniston, Courtney Cox-Arquette, and Lisa Kudrow are all excellent in these scenes though, each of their expressions of disgust is completely different and yet completely fitting to their character.
But this episode's best plotline is that of the college reunion -- or, truthfully, the flashbacks that correspond. They, too, ascend in humor (although, the hair is funniest the first time around) as Ross and Chandler trump each other with college indiscretions (Chandler absolutely wins this -- he comes off looking like a pimp next to Ross -- not only did he make out with Missy "all the time", he got Rachel!) But Rachel and Monica's cameo make the flashbacks, truly, with their awful dancing and... well, antics, I suppose. The climax is, of course, Monica and Ross discovering that they kissed each other. Matthew Perry is excellent comedic contrast to their incredulity. But the actual reunion scenes are really just setup, and frankly weren't terribly interesting. Definitely worth it, though.
The "little funny" (as my sister and I like to call it) at the end is perfect -- Monica, in the fatsuit, dancing. Oh, my sides are aching.