@Swag Wagon
I know this is an old comment, but SonaAhri and ZacRiven didn't come from nowhere. This is old lore, but Sona's a spirit or is connected to the spirit world or something and people on the physical plane can't hear her. Them, she's just a mute musician. Ahri is a forest spirit and can hear entities from the spirit world, which would include Sona. They don't interact in the canon, even post-rework, but the lines are there and the fandom connected them.
ZacRiven is a major notp for me, but it does come from somewhere, technically. Riven's worst skin (Battle Bunny) features an oddly Zac-shaped blob in the splash-art's background. Since it was before his release, people thought it was a future ghost champion. Turns out it was just a blob dude. But they "share" a splash art, so that's where that pairing came from.
And I guess Rosa and Hilda are from the same series? W&B and W&B2? I haven't played them, but since they're part of the same line, that would make sense why people ship the protags/characters from them. But very much more of a crack ship than the other two ships.