I don't know if it's fair to call Weezer the Grandpappy of Nerd Music, but they were certainly the first band I came across that foregrounded the kind of nerdy experience I was having, and for me, they were certainly the most impactful.
I was at what was basically a summer camp for geeks in 1994, and somebody had a copy of the DGC Rarities, Vol. 1 CD with Weezer's "Jaime" on it. I fell in love with their sound, and somebody else down at the end of the hall had Weezer, and a small group of us all kind of discovered the band together.
For a bunch of 13- and 14-year-olds (boys and girls) who were all kind of terrified of romantic relationships, hearing a band (on the same label as Nirvana!!) sing about being awkward around the opposite sex, holing up in your room listening to records (like we were doing right at that moment as we listened to them!), reading comics and playing D&D, it felt like the kind of band we would have been in if we'd been able to write or play music at all.
And then they blew up with songs like "Undone" and "Buddy Holly." Their success reinforced the idea that we were weird, but we were not alone.
And Weezer was also surprisingly heavy. So where Nirvana was my gateway band into metal (and I got WAY into metal by 1996), when Pinkerton came out and it was distorted and full of feedback and legit heavy but still with the catchy songwriting of Weezer, I happily still listened to Weezer alongside your Sepultura and your At the Gates and your Acid Bath.
More important than how Pinkerton sounded, though, was what it was about. More than anything, it validated Rivers Cuomo as "one of us." He was now this internationally famous rock star, but the first song on the record is called "Tired of Sex," and it wasn't about how great being a rock star was, it was about how even when you're surrounded by women and fame and money, inside you're still the same awkward kid that feels better/safer in your room. I guess on some level maybe that's a bummer, but for me, and a lot of my friends at the time, it wasn't. It felt like the opposite.
About a year later, I had a roommate who played guitar, and I started trying to teach myself to play. I'd been playing drums in metal bands for a few years by that point, but no guitar. So I downloaded a bunch of tabs from this new Internet thing, and I taught myself about half of Pinkerton. This one was fun to play sitting on the West Mall at the University of Texas:
And then Weezer went away. When they came back, Rivers Cuomo disavowed my beloved Pinkerton in interviews, and they were never the same. But that's ok. It was pretty great while it lasted.
And finally, as an aside, Pinkerton is also the source of my favorite-ever misunderstood lyric. For a long time, one of my friends thought the line "Why bother? It's gonna hurt me / It's gonna kill when you desert me" was "My father is gonna hurt me / He's gonna kill when you desert me." Sure, the song is actually called "Why Bother?" and why somebody's father would kill them if their girlfriend left was a mystery. but it made the song way, way darker.