Another Sweathog has gone to heaven: Actor Ron Palillo, who played the needy, nerdy Arnold Horshack on ABC’s mid-seventies smash high-school-set sitcom Welcome Back, Kotter, died today at the age of 63. Kotter never got passed from generation to generation like, say, The Brady Bunch, so when the news started trickling out over Twitter and Facebook this morning, those born after Jimmy Carter took office likely shrugged uncomprehendingly or, if in procrastination mode, made a detour to Google to ask “What’s a Horshack?” But Palillo’s passing, which follows the January death of fellow Sweathog Robert Hegyes (Epstein), gave Gen X-ers a sad pause in the day as they went rushing to YouTube (today’s pop-culture group mourning spot) to search for clips of him honking his Eddie Murphy–like laugh.

Palillo’s Horshack — one of the underachieving crew of Mr. Kotter’s students called the Sweathogs, led by John Travolta’s Vinnie Barbarino — was neither beloved (Fonzie) nor groundbreaking (George Jefferson). But both he and Welcome Back, Kotter were absolutely iconic for Dynamite-reading, ABC-watching kids and teens growing up in the seventies. While the show never cracked Nielsen’s top ten, it was hugely popular with youth; the Alphabet network rode to the top of the ratings at decade’s end by relentlessly catering to this previously underserved demo. From Happy Days to Mork & Mindy and Charlie’s Angels, ABC was where pop culture lived for those under 25 during the mid to late seventies. (They made board games out of ABC shows and celebrated them with song parodies!) Horshack was the pre-Screech, the nerdy loser who somehow got to hang out with the cool kids and was accepted as one of the gang. Today’s kids have Glee and The Big Bang Theory, series built around celebrating the “losers” of the world. But in the days before “It Gets Better” and “Flip the Script,” decidedly multi-cultural sitcoms like Kotter and characters like Horshack sent a (very) subtle message to younger viewers that it was okay to hang with those a bit different. True, this social engineering was well hidden beneath the broadest of humor and the corniest of catchphrases (“Oooh! Oooh! Oooh!” Horshack would bark as he raised his hand to be called on). America’s teens and preteens tuned in for Horshack’s car-horn guffaw, his vaudevillian one-liners, his comically desperate need for attention. The notion that a geeky, decidedly un-hunky pipsqueak could roll with the smooth Sweathogs of the world was an underappreciated bonus. And for this reason alone, Horshack mattered. Just a little.