I also think Pokemon should get a shout-out. I'm a late Millennial so I was already an older teen when Pokemon came out, but I played the original Pokemon Red on the original Gameboy and watched the fist season or two of the TV show since it aired after school when I was doing homework. My kids who are Gen Zers watched the latter Pokemon seasons and movies and play all the current Pokemon games. So I'd argue if not the TV show, the Pokemon franchise has been able to span multiple generations. It's part of the reason why Pokemon GO exploded initially and became such a phenom. Ironically it's now mostly the older Millennials that still play that game.
EDIT: I've also never seen a single episode of Spongebob. Obviously I've heard of it, but it came after my time and it never really looked interesting to me. I think Spongbob is definitely a young Millennial thing with a pretty sharp dividing line.