>>That's an expression I picked this week and liked it immediately. Short, descriptive, to-the-point, unambiguous (unless you thought I'd say "and they look even better when swirls are in full blossom").
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>But that doesn't answer my Q or explain what they are.

The small neon bulbs of the screw-in type, where the glass tube is mostly helicoidal (i.e. like a screw line, a twirl, a slinky, a corkscrew).

>>Does that mean that when you want to switch to one of these, you need to replace the whole fixture (or at least the socket)? If that's the case, I'd rather skip them and go straight to LEDs.
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>That's what I want to know: the LEDs have the same conical shape (like a landing module) as the halogens, and the same bayonet, so would fit in the halogen light socket, but I don't know if they'd work. The main hal fitting we have has the trafo in the ceiling rose, with the bulbs on branches. Also i want to replace the ceiling spots in the lounge but didn't fancy going halogen there too, so now I know a tasty alternative for totally replacing those lights in LEDs.

Ah then if you have those low-voltage movable halogens on a bar, that you can move along, they may operate on quite a different voltage than your LEDs. You better check the specs on both - I'm not sure that's anywhere near compatible. Why would it be - this is capitalism. They have to make money each time. You buy everything anew.