I first remember knowing about Nickelodeon in 1991 or 1992. My aunt and uncle had cable, and when I saw Nickelodeon, I really wanted cable (and my household finally got cable in 1992!). But before getting cable I did get to see some of the programming at other people's houses. Some of the first things I remember seeing on Nickeloden were the original three Nicktoons, Looney Tunes, Inspector Gadget, Heathcliff, and certain Nick at Nite shows (Best of SNL, Mister Ed, Mork and Mindy, Bewitched). When I finally got cable, I feel like I watched Nickelodeon all the time (though I know that's not true). There's hardly a show on the channel that I didn't watch, even if I still did watch other channels and did other things besides watch TV.
I remember learning a bit about the channel's '80s history in 1999, when the 20th anniversary was beginning. Around that time Nickelodeon had a weekend-long anniversary marathon, featuring many shows no longer on the channel. I had seen it pointed out that this marathon did NOT include anything from the very early years of the channel, making me a little disapointed, because I really wanted to see Pinwheel and those other shows. But now I don't have the same desire to see all those shows anymore (I've caught a little bit of Pinwheel on youtube, but don't think I've ever gotten through a whole YouTube clip). Though I do enjoy watching the '80s promos online.
There's a lot I'd like to talk about, but don't have much time right now. I'd like to say that Welcome Freshmen seems to be a very underrated show. I've found onlly one full episode, "Money", on youtube (there's another episode, "The People Versus Walter", which for some reason is only the first half and the end credits. I'd like to know how that episode ended!). The Nostalgia Critic didn't mention it in his "Nickelodeon Month" (likely he couldn't find any footage), it's one of the few '90s Nick shows not on iTunes in any way (there's a number of iTunes releases called the "Nick Rewind" collection, featuring random episodes from different shows, and that's not even included... And yet episodes of "As Told By Ginger" and "Rocket Squad" are???). TV Tropes doesn't even have a page for the show. But at the time that was one of my favorite live-action Nick shows, along with Salute Your Shorts and Nick Arcade.