Yeah, the clamp-on roller skate - turned skateboard. I think that idea goes back to the pre-WWII years and although California is likely the home of the first such contraption, they seemed to spring up in any port city that handled citrus fruit. There's a picture of my dad with a citrus crate scooter (orange crate, label and all, nailed atop the skateboard as a "handlebar") near the river in New Orleans, where he grew up. Some woman that lived up the street would scatter gravel on the sidewalks to keep the noisy metal-wheeled scooters away, but they figured out how to attach an angled board to the front, skimming low over the sidewalk, that would shove all the gravel off of the concrete.