The first online fad I remember experiencing was “The Colossal Cave Adventure” and “Zork”, both on a VAX VMS mainframe system to which I connected at 300 bps from my Uncle’s PC.
The first www fad I remember was Hamsterdance.
The Dancing Baby could do the Macarena! That’s so trendy!
I remember mIRC chat rooms. That was the coolest thing. What a way to hook up with people of the opposite sex, that was. I’m sure chat rooms still exist somewhere, but I haven’t bothered to seek one out in years.
I also remember web addresses having to have the “http://” in front of them on advertisements. And explaining it verbally, That’s H. T. T. P. Colon. front-slash. front-slash. That’s two front-slashes. Then W, W, W,…"
Geocities and Tripod! I just googled them and they both still exist.
As far as earliest trends, I would have to say using HTML code in chat to make oneself out to be a hacker. “Ha, my text is blue! I am the reigning king!” But if we can’t count that, I would say 1447 5p34k! Or “leet speak,” to all of you miserly technophobes!
I was a regular - and among the first 50 account holders - at one of the earliest Internet cafes, the Speakeasy in Seattle, in 1994. I even unofficially worked there for a couple of months. Old-skool Unix, yo.
I will never be able to give up my Speakeasy account. On the rare occasion I call tech support and give my member number, they do a little “whoa…” 
I IRC (“irkata”) every day. 
The dialing modem sound. It was used on anything to signify modernity.
ASCII art, of course.
Chain emails with curses or blessings for spreading them.
I know. Orrie still limps along. Every few months, we talk about revamping the website and adding a bulletin board, but none of us has the time to commit to such a project.
I remember one year – early 90s I think – that people were e-mailing something called an “animated Christmas card.” It was an ASCII-art thing that would display a Christmas tree with various animated effects (twinkling lights, etc.) on a color video (dumb) terminal.
Unfortunately, it only worked on a certain, specific kind of terminal configuration. On any other hardware it just displayed as endless screens of gibberish. I remember getting about ten copies of that thing; and when I told people it didn’t work on my terminal, they’d just send another copy and say “try it now.” One person posted it to a huge LISTSERV list, and when it didn’t work for everyone, posted it again and again and again.
I’ve been on the net in one capacity or another since 1976 (on my dad’s TRS-80 with “The Source,” that later became Compuserve (though at $9.95 an hour I wasn’t allowed to spend much time there!)) But the first real internet memes I remember were “Mr. T Ate My Balls” and the whole Kibo thing on Usenet.
I forgot a big one that I don’t think was mentioned in this thread.
Badger badger badger badger badger …
I had totally forgotten about the “_____ Ate My Balls” fad. I recall Mr. T and Chewbacca, and then it’s all a blur.
Before this thread reminded me of that, I was going to mention “cow orker”. When it first appeared, people thought it was hilarious. Way more than it deserved.
I submitted a site to Mirsky’s Worst of the Web, and he put it up for that week. It was a UFO/Area 51 “conspiracy theory” site, that also had numerous links to “how to pick up women” sites. Gee, whoda thunk it, UFO conspiracy nuts have a hard time meeting women…
Shake, geezer. I remember reading the Scientific American article on Life and writing a program to run it.
I think I actually participated in the “do balrogs have wings” flamewar on rec.arts.books.tolkien (circa 1998).
Compuserve. ick.
Flame wars on private BBS’s, over dialup.
For me, the first really big one would probably be (lyrics): Mi-a-hii Mi-a-huu Mi-a-haa Mi-a-ha ha.
That was the first big thing I encountered as an in-depth internet user. Gasp in awe at my youth.
Implementing the game of Life was the final project in my assembly language class. You had to make it run without the monitoring flickering for an A. The machine we ran on was the MIT PDP-1 where Spacewar was invented. Not much to do with the Internet though.
In 1995 I started grad school and got my first e-mail address. Within a week or so I got an e-mail about the Good Times virus. In a panic, I immediately forwarded it to everyone I knew who had an e-mail address. Fortunately, this was only maybe four people.
Incidentally, anyone who’s drawn to a thread like this has GOT to watch this video. It’s a made-up “unaired pilot” for the show 24, supposedly shot in 1994. Full of great little details about how things have changed.
Not really a fad but the first thing I was really into on the net was Babylon 5 ('95/'96). I used to read up on upcoming episodes (that would take months to air on this side of the atlantic) and read all about the characters and alien races in the B5 universe. That was before I discovered porn and SDMB.
Green Card Spam
net.legends FAQ
Clarence Thomas III
Ah, I was going to post about the “WAZZZUUUUUP!” bit, but your post reminds me of something WAY earlier.
Back when I had to check my email on PINE, messages would go around with animated ASCII art. You had to hold “PGDN”, and each “frame” of the animation was exactly as many lines as the number of lines PINE could display on the screen at once.
Ingenius, I might even go as far as saying…
but then different email versions came out with different numbers of lines… grr.